History and Scope of Epidemiology

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONHistory andNOT FOR Scope SALE OR DISTRIBUTION of Epidemiology © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION LEARNING OBJECTIVES

By the end of this chapter the reader will be able to:

© Jones define & Bartlettthe term epidemiology Learning, LLC © Jones & Bartlett Learning, LLC NOT FORdefine SALE the components OR DISTRIBUTION of epidemiology (determinants, distribu-NOT FOR SALE OR DISTRIBUTION tion, morbidity, and mortality) name and describe characteristics of the epidemiologic approach discuss the importance of Hippocrates’ hypothesis and how it dif- © Jones & Bartlett Learning,fered from the LLC common beliefs of the time © Jones & Bartlett Learning, LLC NOT FOR SALE OR discuss DISTRIBUTION Graunt’s contributions to biostatisticsNOT FOR and howSALE they OR DISTRIBUTION affected modern epidemiology explain what is meant by the term natural experiments, and give at least one example © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONCHAPTER OUTLINE NOT FOR SALE OR DISTRIBUTION

I. Introduction II. Epidemiology Defined III. Foundations of Epidemiology © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC IV. Historical Antecedents of Epidemiology NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION V. Recent Applications of Epidemiology VI. Conclusion VII. Study Questions and Exercises © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 1

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2 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC IntroductionNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Controversies and speculations regarding the findings of epidemiologic research are frequent topics of media reports; these findings sometimes arouse public hysteria. Examples of the questions raised by media reports include: “Is it more © Jones & Bartlettdangerous Learning,to vaccinate anLLC entire population against smallpox© Jones (with & Bartlettresulting Learning, LLC NOT FOR SALEcomplications OR DISTRIBUTION from the vaccine) or to risk infectionNOT with FORthe disease SALE itself OR DISTRIBUTION through a terrorist attack?” “Is Ebola virus a danger to the general public?” “Should I give up eating fatty foods?” “Is it safe to drink coffee or alcoholic bev- erages?” “Will chemicals in the environment cause cancer?” “Should one pur- © Jones & Bartlett Learning,chase bottled LLC water instead of consuming© Jones tap &water Bartlett from public Learning, drinking LLC NOT FOR SALE OR DISTRIBUTIONsupplies?” Will medications for chronicNOT diseases FOR such SALE as diabetes OR DISTRIBUTIONcause harmful side effects?” “Will the foods that I purchase in the supermarket make me sick?” Consider a major outbreak of Escherichia coli (E. coli) infections that affected multiple states in the United States and captured media headlines for several months.© Jones The 2006 & Bartlett outbreak becameLearning, a mystery LLC that gradually unfolded over© timeJones & Bartlett Learning, LLC (ExhibitNOT 1–1).FOR Initially, SALE the OR outbreak DISTRIBUTION was linked to prepackaged spinachNOT as the FOR SALE OR DISTRIBUTION most likely vehicle. The spinach was traced back to its source, Natural Selection Foods near Salinas, California. The mechanism for contamination of the spinach with E. coli bacteria was never established definitively. © Jones & BartlettEpidemiologic Learning, research LLC methods are a powerful tool for© studyingJones health& Bartlett in the Learning, LLC population. In many instances, epidemiology resembles detective work, because NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the causes of disease occurrence are often unknown. Exhibit 1–1 raises several issues that are typical of many epidemiologic research studies:

When there is a linkage or association between a factor (i.e., as contami- © Jones & Bartlett Learning,nants LLC in food and water) and ©a health Jones outcome, & Bartlett does this Learning, observation LLC NOT FOR SALE OR DISTRIBUTIONmean that the factor is a cause ofNOT disease? FOR SALE OR DISTRIBUTION If there is an association, does the amount of disease vary according to the amount of exposure to the factor? Based on the observation of such an association, what practical steps should individuals and public health departments take? What should the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC individual consumer do? NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Do the findings from an epidemiologic study merit panic or a measured response? How applicable are the findings to settings other than the one in which the research was conducted? What are the policy implications of the findings? © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEIn this OR chapter DISTRIBUTION as well as in later chapters of this book,NOT we answerFOR theSALE forego- OR DISTRIBUTION ing questions. We discuss the stages that are necessary to unravel mysteries about

I NTRODUCTION 3

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORE. coliSALEO157:H7 OR DISTRIBUTION Associated with NOT FOR SALE OR DISTRIBUTION Prepackaged Spinach: A Mysterious and Unsolved Problem

© Jones & Bartlett Learning,E. coli O157:H7 LLC is a bacterial agent that can© be Jones ingested & in Bartlett contam- Learning, LLC NOT FOR SALE OR inatedDISTRIBUTION food. E. coli refers to Escherichia coli, aNOT bacterium FOR that SALE includes OR DISTRIBUTION EXHIBIT 1–1 some strains that are normal inhabitants of the intestines of human beings as well as animals. The form of this bacterium known as E. coli O157:H7 can act as an enteric pathogen, which can produce bloody © Jones & Bartlett Learning,diarrhea LLC and, in some instances,© the Jones hemolytic-uremic & Bartlett syndrome Learning, (HUS), LLC a NOT FOR SALE OR DISTRIBUTIONtype of kidney failure. Severe casesNOT of E. FOR coli O157:H7 SALE can OR be DISTRIBUTION fatal. An outbreak of E. coli O157:H7 in the late summer and early fall of 2006 sickened 199 persons across the United States and caused three deaths (as of October 6, 2006, when the outbreak appeared to have subsided). The © 2006Jones outbreak & Bartlett caused Learning,102 (51%) of LLCthe ill persons to be hospitalized;© Jones 31 & Bartlett Learning, LLC patients (16%) were afflicted with HUS. The majority of cases (141, 71%) NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION were female. A total of 22 children under 5 years of age were affected.1 Data reported before October 6 indicated that the frequency of cases peaked from August 30 to September 1 (Refer to Figure 1–1a).2 Two of the

20 First confirmed case in a person reporting 15 fresh spinach © Jones & Bartlett Learning, LLC consumption© Jones & Bartlett Learning, LLC 10 (August 19) NOT FOR SALE OR DISTRIBUTION Number of Cases NOT FOR SALE OR DISTRIBUTION

0 2 468101214 16 18 20 22 24 26 28 30 1 3 5 7 9 11 13 Aug. Sept. © Jones & Bartlett Learning,Day LLC and Month © Jones & Bartlett Learning, LLC

NOT FOR SALE*Confirmed ORcases withDISTRIBUTION known dates of illness onset reported as of NOT FOR SALE OR DISTRIBUTION 1:00 p.m. EDT on September 26, 2006. FIGURE 1–1 (a) Number of confirmed cases (n 171) of Escherichia coli serotype O157:H7 infection, by date of illness onset © Jones & Bartlettin the Learning, United States LLC from August to September© 2006. Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALEcontinues OR DISTRIBUTION

4 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC EXHIBITNOT FOR 1–1 SALEcontinued OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION deaths occurred among elderly persons and one among a 2-year-old child. The outbreak spread across 26 U.S. states; Ohio, Utah, and Wisconsin reported the greatest number of cases (Figure 1–1b). © Jones & BartlettTracking Learning, down the originsLLC of the outbreak required© Jonesextensive & detective Bartlett Learning, LLC NOT FOR SALEwork. OR First, DISTRIBUTION attention turned to the possible sourceNOT of the FOR infection. SALE On OR DISTRIBUTION September 13, 2006, epidemiologists in Wisconsin and Oregon reported to the Centers for Disease Control and Prevention (CDC) that fresh spinach was suspected as the source. Similarly, epidemiologists in New © Jones & Bartlett Learning,Mexico LLC reported that raw spinach ©was Jones associated & Bartlett with a cluster Learning, of E. coli LLC NOT FOR SALE OR DISTRIBUTIONO157:H7 cases. By using a methodNOT of genetic FOR SALEfingerprinting OR DISTRIBUTION known as pulsed-field gel electrophoresis, CDC officials confirmed that some strains of E. coli O157:H7 were present in materials isolated from the patients. As of September 26, 2006, 123 of 130 patients reported that they had consumed© Jones raw fresh& Bartlett spinach Learning,during the 10-day LLC interval before becoming© ill. Jones & Bartlett Learning, LLC InvestigatorsNOT FOR SALEobtained OR three DISTRIBUTION open bags of spinach consumed byNOT the FOR SALE OR DISTRIBUTION patients and confirmed the presence of E. coli O157:H7. The U.S. Food and

WA © Jones & Bartlett Learning, LLC © Jones & MEBartlett Learning, LLC OR MN NOT FOR SALE OR DISTRIBUTIONID WI NOT FORNY SALE OR DISTRIBUTION WY MI CT PA NE NV OH UT IL IN DC MD CO WV CA VA KY © Jones & Bartlett Learning, LLC © Jones &TN Bartlett Learning, LLC AZ NOT FOR SALE OR DISTRIBUTION NM NOT FOR SALE OR DISTRIBUTION

1–4 5–9 10–14 15 or higher © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTFIGURE FOR 1–1 SALE(b) Distribution OR DISTRIBUTION of cases across the United States.NOT FOR SALE OR DISTRIBUTION Source: From Centers for Disease Control and Prevention. Ongoing multistate outbreak of Escherichia coli serotype O157:H7 infections associated with consumption of fresh spinach—United States, September 2006. MMWR. 2006;55:1045–1046. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR continuesSALE OR DISTRIBUTION

I NTRODUCTION 5

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTEXHIBIT FOR 1–1 SALEcontinued OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Drug Administration (FDA) issued a warning to consumers not to eat bagged fresh spinach. Next, the investigation turned to identifying the growers of the spinach © Jones & Bartlettand any Learning, environmental LLC factors that could have caused© Jones the fresh & spinach Bartlett to Learning, LLC NOT FOR SALEbecome OR DISTRIBUTION contaminated with E. coli O157:H7. TheNOT FDA FOR linked SALE the raw OR DISTRIBUTION spinach involved in the outbreak to Natural Selection Foods LLC of San Juan Bautista, California.3 The producer announced a recall of spinach on September 15, 2006. The FDA and State of California conducted a trace © Jones & Bartlett Learning,back LLC investigation, which implicated© Jones four ranches& Bartlett in Monterey Learning, and San LLC NOT FOR SALE OR DISTRIBUTIONBenito Counties.4 Cattle feces fromNOT one FOR of the SALE four ranches OR DISTRIBUTION contained a strain of E. coli O157:H7 that matched the strain that had contaminated the spinach as well as the strain found in the 199 cases. Noteworthy is the fact that subsequent to this major outbreak, E. coli © O157:H7Jones & continues Bartlett to Learning,threaten the foodLLC supply of the United States,© Jones not & Bartlett Learning, LLC NOTonly FOR from spinachSALE butOR also DISTRIBUTION from other foods. During November throughNOT FOR SALE OR DISTRIBUTION December 2006, Taco Bell restaurants in the northeastern United States experienced a major outbreak that caused at least 71 persons to fall ill. The source of the outbreak was not established clearly.5 Contamination of © Jones & BartlettTopp’s Learning, brand frozen LLC ground beef patties and Totino’s© Jones or Jeno’s &brand Bartlett pizzas Learning, LLC NOT FOR SALEwith OR E. DISTRIBUTIONcoli O157:H7 is believed to have sickened moreNOT than FOR 60 residentsSALE ORof DISTRIBUTION the eastern half of the United States during summer and early fall 2007.

© Jones & Bartlett Learning,diseases, LLC such as those due to environmental© Jones exposures& Bartlett or those Learning, for which LLC the NOT FOR SALE OR DISTRIBUTIONcause is entirely unknown. NOT FOR SALE OR DISTRIBUTION Epidemiology is a discipline that describes, quantifies, and postulates causal mechanisms for health phenomena in populations. Using the results of epidemiologic studies, public health practitioners are aided in their quest to control health ©problems Jones such & Bartlettas disease outbreaks.Learning, The LLC investigation into the E. coli©outbreak Jones & Bartlett Learning, LLC NOTillustrates FOR some SALE of the classicOR DISTRIBUTION methods of epidemiology: first, describingNOT all of theFOR SALE OR DISTRIBUTION cases, enumerating them, and then following up with additional studies. Exhibit 1–1 illustrates the extensive detective work involved in identifying the cause of a disease outbreak. The hypothesized causal mechanism that was ultimately linked © Jones & Bartlettto contaminated Learning, spinach LLC was the bacterium E. coli. All© of Jones the features & Bartlett described inLearning, LLC NOT FOR SALEthe investigationOR DISTRIBUTION are hallmarks of the epidemiologicNOT approach. FOR In SALEthis example, OR DISTRIBUTION the means by which E. coli contaminated the spinach remains an unresolved issue.

6 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC EpidemiologyNOT FOR SALE OR Defined DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The word epidemiology derives from epidemic, a term that provides an immediate clue to its subject matter. Epidemiology originates from the Greek words epi (upon) demos (people) logy (study of). Although some conceptions of epi- © Jones & Bartlettdemiology Learning,are quite narrow, LLC we suggest a broadened scope© Jones and propose & Bartlett the fol- Learning, LLC NOT FOR SALElowing definition:OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Epidemiology is concerned with the distribution and determinants of © Jones & Bartlett Learning,health LLC and diseases, morbidity, injuries,© Jones disability, & andBartlett mortality Learning, in popula- LLC tions. Epidemiologic studies are applied to the control of health problems NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION in populations. The key aspects of this definition are determinants, distribution, population, and health phenomena (e.g., morbidity and mortality).

Determinants© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC DeterminantsNOT FOR are SALE factors orOR events DISTRIBUTION that are capable of bringing about a changeNOT in FOR SALE OR DISTRIBUTION health. Some examples are specific biologic agents (e.g., bacteria) that are associated with infectious diseases or chemical agents that may act as carcinogens. Other potential determinants for changes in health may include less specific factors, such © Jones & Bartlettas stress or adverseLearning, lifestyle LLC patterns (lack of exercise or a diet© Joneshigh in saturated & Bartlett fats). Learning, LLC NOT FOR SALEThe following OR DISTRIBUTION four vignettes illustrate the concern of epidemiologyNOT FOR with SALE disease OR DISTRIBUTION determinants. For example, consider the steps taken to track down the source of the bacteria that caused anthrax and were sent through the mail; contemplate the position of an epidemiologist once again. Imagine a possible scenario for describ- © Jones & Bartlett Learning,ing, quantifying, LLC and identifying the determinants© Jones for& eachBartlett of the vignettes.Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Case 1: Intentional Dissemination of Bacteria That Cause Anthrax © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC After the United States experienced its worst terrorist attack on NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION September 11, 2001, reports appeared in the media about cases of anthrax in Florida beginning in early October. In the United States, anthrax usually affects herbivores (livestock and some wild animals); human cases are unusual. Anthrax is an acute bacterial disease caused © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC by exposure to Bacillus anthracis. Cutaneous anthrax affects the skin, pro- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION continues

E PIDEMIOLOGY D EFINED 7

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTCASE FOR 1 continued SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ducing lesions that develop into a black scab. Untreated cutaneous anthrax has a case-fatality rate of 5% to 20%. The much more severe inhalational form, which affects the lungs and later becomes dissemi- © Jones & Bartlettnated Learning, by the bloodstream, LLC has a high case fatality© rate. Jones6 Observations & Bartlett of Learning, LLC NOT FOR SALE anOR alert DISTRIBUTION infectious disease specialist along with theNOT support FOR of laboratorySALE OR DISTRIBUTION staff led to the suspicion that anthrax had been deliberately sent through the postal system.7 The CDC, in collaboration with officials at the state and local levels, identified a total of 21 anthrax cases (16 confirmed and © Jones & Bartlett Learning, fiveLLC suspected) as of October© 31,Jones 2001. & The Bartlett majority Learning, of the cases LLC NOT FOR SALE OR DISTRIBUTIONoccurred among employees locatedNOT in FOR four areas: SALE Florida, OR NewDISTRIBUTION York City, New Jersey, and the District of Columbia.8–11 Figure 1–2 portrays the distribution of the 21 cases in four geographic areas of the United States.

© Jones & Bartlett Learning,As of October LLC 31, 2001, © Jones & Bartlett Learning, LLC 21 cases were reported NOT FOR SALE OR DISTRIBUTIONin four states. There was NOT FOR SALE OR DISTRIBUTION one isolated case in Connecticut (not linked to any exposure source).

Florida (2 cases) New York City (7 cases) New Jersey and District of Columbia (5 © Jones & BartlettWorkers Learning, at America Media,Inc. LLC6 cutaneous cases (3 Pennsylvania (7 cases,© Jones 5 cases, all &inhalational) Bartlett 4 cases Learning, LLC First case was a 63-year-old confirmed, 3 suspected) in 4 confirmed, and 2 suspected). in D.C. postal facility. 1 case worker who died from media companies. One of the 5 cases at a New Jersey in U.S. State Department mail NOT FOR SALE ORinhalational DISTRIBUTION anthrax. Second 6 cases involved suspected postal facility. No specificNOT FORfacility: This SALE facility receives OR DISTRIBUTION case identified in coworker mail room contact with a letter contaminated letters identified, mail from the D.C. facility that with positive nasal sample. that contained anthrax. 1 but contaminated mail had 4 cases. Environmental sample from inhalation case (confirmed): suspected to have passed workplace tested positive for patient worked in a hospital through facility. anthrax. stockroom.

© Jones & Bartlett Learning,FIGURE LLC 1–2 Occurrence of© anthrax Jones cases & Bartlett during the Learning, 2001 LLC NOT FOR SALE OR DISTRIBUTIONterrorist incident according toNOT the investigation FOR SALE by ORthe Centers DISTRIBUTION for Disease Control and Prevention.

© Jones & BartlettCase Learning, 2: Outbreak LLC of Fear © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION When a 36-year-old lab technician known as Kinfumu checked into the general hospital in Kikwit, Zaire, . . . complaining of diarrhea and a fever, anyone could have mistaken his illness for the dysentery that was © Jones & Bartlettplaguing Learning, the city. Nurses,LLC doctors, and nuns did ©what Jones they could & Bartlett to help Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION continues

8 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC CASENOT 2 FORcontinued SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the young man. They soon saw that his disease wasn’t just dysentery. Blood began oozing from every orifice in his body. Within four days he was dead. By then the illness had all but liquefied his internal organs. © Jones & BartlettThat Learning,was just the beginning. LLC The day Kinfumu died,© aJones nurse and & aBartlett nun Learning, LLC NOT FOR SALEwho OR had DISTRIBUTIONcared for him fell ill. The nun was evacuatedNOT to anotherFOR SALE town OR DISTRIBUTION 70 miles to the west where she died—but not until the contagion had spread to at least three of her fellow nuns. Two subsequently died. In Kikwit, the disease raged through the ranks of the hospital’s staff. © Jones & Bartlett Learning,Inhabitants LLC of the city began fleeing© toJones neighboring & Bartlett villages. Learning,Some of the LLC NOT FOR SALE OR DISTRIBUTIONfugitives carried the deadly illness NOTwith them. FOR Terrified SALE health OR DISTRIBUTIONofficials in Kikwit sent an urgent message to the World Health Organization. The Geneva-based group summoned expert help from around the globe: a team of experienced virus hunters composed of tropical-medicine spe- ©cialists, Jones microbiologists, & Bartlett Learning,and other researchers. LLC They grabbed their ©lab Jones & Bartlett Learning, LLC NOTequipment FOR andSALE their OR bubble DISTRIBUTION suits and clambered aboard transportNOT FOR SALE OR DISTRIBUTION planes headed for Kikwit.12

On normal workdays, the streets of New York City’s garment district are lively canyons bustling with honking trucks, scurrying buyers, and sweat- © Jones & Bartlett Learning,ing rackLLC boys pushing carts loaded© Joneswith suits, & coats,Bartlett and dresses.Learning, But LLC NOT FOR SALE OR DISTRIBUTIONduring September 1978 a tense newNOT atmosphere FOR SALE was evident. OR DISTRIBUTIONSanitation trucks cruised the side streets off Seventh Avenue flushing pools of stag- nant water from the gutters and spraying out disinfectant. Teams of health officers drained water towers on building roofs. Air conditioners ©fell Jones silent for & inspection,Bartlett Learning, and several chillingLLC signs appeared on 35th© Jones & Bartlett Learning, LLC NOTStreet: FOR “The SALENew York OR City DISTRIBUTION Department of Health has been advisedNOT of FOR SALE OR DISTRIBUTION possible causes of Legionnaires’ disease in this building.” By the week- end, there were six cases of the mysterious disease, 73 more suspected and two deaths. In the New York City outbreak, three brothers were the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR continuesSALE OR DISTRIBUTION

E PIDEMIOLOGY D EFINED 9

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTCASE FOR 3 continued SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION first victims. Carlisle, Gilbert, and Joseph Leggette developed the fever, muscle aches, and chest congestion that make the disease resemble pneumonia. Joseph and Gilbert recovered; Carlisle did not. “He just got © Jones & Bartlettsick andLearning, about a week LLC later he was dead,” said ©John Jones Leggette, & Bartletta fourth Learning, LLC NOT FOR SALEbrother OR DISTRIBUTION who warily returned to his own job in theNOT garment FOR district SALE the OR DISTRIBUTION next week. “I’m scared,” he said. “But what can you do?”13

From January 1 to March 10, 1980, Eastern Airlines received 190 reports © Jonesof episodes & Bartlett of red spots Learning, appearing on LLC the skin of flight attendants© (FAs) Jones & Bartlett Learning, LLC NOTduring FOR various SALE flights. OR DISTRIBUTIONComplaints of symptoms accompanyingNOT the FOR SALE OR DISTRIBUTION spots were rare, but some FAs expressed concern that the spots were caused by bleeding through the skin and might indicate a serious health hazard. On March 12, investigators from the CDC traveled to Miami to © Jones & Bartlettassist Learning, in the investigation. LLC No evidence of damage© to Jones underlying & Bartlettskin was Learning, LLC NOT FOR SALEnoted OR DISTRIBUTIONon these examinations, nor was any notedNOT by consultant FOR SALE derma- OR DISTRIBUTION tologists who examined affected FAs after the spots had disappeared. Chemical tests on clinical specimens for the presence of blood were neg- ative. Airline personnel had investigated the ventilation systems, clean- © Jones & Bartlett Learning,ing LLC materials and procedures,© andJones other & environmental Bartlett Learning, factors on LLC NOT FOR SALE OR DISTRIBUTIONaffected aircraft. Airflow patternsNOT and FOR cabin SALE temperatures, OR DISTRIBUTION pressures, and relative humidity were found to be normal. Cleaning materials and routines had been changed, but cases continued to occur. Written reports by FAs of 132 cases occurring in January and February showed © Jonesthat 91 different& Bartlett FAs hadLearning, been affected, LLC 68 once and 23 several times.© Jones & Bartlett Learning, LLC NOTOf FORthese cases, SALE 119 OR (90%) DISTRIBUTION had occurred on a single type of aircraft.NOT Of FOR SALE OR DISTRIBUTION the 119 cases from implicated aircraft, 96% occurred on north- or south-bound flights between the New York City and Miami metropoli- tan areas, flights that are partially over water. Only rarely was a case © Jones & Bartlettreported Learning, from the LLC same airplane when flying transcontinental© Jones & Bartlettor other Learning, LLC 14 NOT FOR SALE east-westOR DISTRIBUTION routes. NOT FOR SALE OR DISTRIBUTION

10 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Health departments, the CDC in Atlanta, and epidemiologic researchers fre- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION quently confront a problem that has no clear determinants or etiologic basis. The methods and findings of epidemiologic studies may direct one to, or suggest, particular causal mechanisms underlying health-related events or conditions, such as the four examples cited in the vignettes: anthrax, the suspected outbreak © Jones & Bartlettof Ebola virus, Learning, Legionnaires’ LLC disease, and red spots on airline© Jones FAs. Read & Bartlett the fol- Learning, LLC NOT FOR SALElowing solutionOR DISTRIBUTION to clear up the mystery of Case 4. NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC Solution to Case© Jones 4: Red & BartlettSpots Learning, LLC NOT FOR SALE OR DISTRIBUTIONThe investigation then concentratedNOT on defining FOR SALEthe clinical OR picture DISTRIBUTION more clearly. An Eastern Airlines (EAL) physician, a consultant dermatologist, and a physician from the National Institute for Occupational Safety and Health (NIOSH) rode on implicated flights on March 14 and examined ©three Jones new cases& Bartlett considered Learning, by the EAL LLCphysician and other flight atten-© Jones & Bartlett Learning, LLC NOTdants (FAs)FOR to SALE be typical OR cases. DISTRIBUTION Although the spots observed consistedNOT of FOR SALE OR DISTRIBUTION red liquid, they did not resemble blood. To identify potential environmental sources of red-colored material, investigators observed the standard activities of FAs on board implicated flights. At the beginning of each © Jones & Bartlettflight FAs Learning, routinely demonstrated LLC the use of life vests,© Jones required &in Bartlettemer- Learning, LLC NOT FOR SALEgency OR landings DISTRIBUTION over water. Because the vests used forNOT demonstration FOR SALE were OR DISTRIBUTION not actually functional, they were marked in bright red ink with the words “Demo Only.” When the vests were demonstrated, the red ink areas came into close contact with the face, neck, and hands of the demonstrator. © Jones & Bartlett Learning,Noting LLC that on some vests the red ©ink Jones rubbed or& flakedBartlett off easily, Learning, investi- LLC NOT FOR SALE OR DISTRIBUTIONgators used red material from the vestsNOT to FOR elicit theSALE typical OR clinical DISTRIBUTION picture on themselves. On preliminary chemical analyses, material in clinical specimens of red spots obtained from cases was found to match red-ink specimens from demonstration vests. On March 15 and 16, EAL removed ©all Jonesdemonstration & Bartlett model lifeLearning, vests from LLCall its aircraft and instructed FAs© Jones & Bartlett Learning, LLC NOTto use FORthe standard, SALE functional, OR DISTRIBUTION passenger-model vests for demonstrationNOT FOR SALE OR DISTRIBUTION purposes. The airline . . . continue[d] to request reports of cases to verify the effectiveness of this action. Although all demonstration vests were obtained from the same manufacturer, the vests removed from specific © Jones & Bartlettaircraft Learning,were noted to LLC vary somewhat in the color© of Jones fabric and & Bartlettin the Learning, LLC NOT FOR SALEcolor OR and DISTRIBUTION texture of red ink, suggesting that manyNOT different FOR production SALE OR DISTRIBUTION lots may have been in use simultaneously on any given aircraft.14

E PIDEMIOLOGY D EFINED 11

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTDistribution FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Frequency of disease occurrence may vary from one population group to another. For example, hypertension may be more common among young African-American men than among young white men. Mortality from coronary 15 © Jones & Bartlettheart disease Learning, may vary LLCbetween Hispanics and non-Hispanics.© Jones Such& Bartlett variations Learning, LLC NOT FOR SALEin disease OR DISTRIBUTION frequency illustrate how disease may haveNOT different FOR distributionsSALE OR DISTRIBUTION depending upon the underlying characteristics of the populations being studied. Population © Jones & Bartlett Learning,Epidemiology LLC examines disease occurrence© Jones among & Bartlettpopulation Learning,groups rather LLCthan among individuals. Lilienfeld16 noted that this focus is a widely accepted feature NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION of epidemiology. For this reason, epidemiology is often referred to as “population medicine.” The epidemiologic and clinical descriptions of a disease are quite different as a result. Note the different descriptions of toxic shock syndrome (TSS), a condition that showed sharp increases during 1980 in comparison to the imme- ©diately Jones previous & Bartlett years. TSS Learning, is a severe illness LLC that in the 1980 outbreak was© Jones found & Bartlett Learning, LLC NOTto be associatedFOR SALE with vaginalOR DISTRIBUTION tampon use. The clinical description of TSSNOT would FOR SALE OR DISTRIBUTION include specific signs and symptoms, such as high fever, headache, malaise, and other more dramatic symptoms, such as vomiting and profuse watery diarrhea. The epidemiologic description would indicate which age groups would be most © Jones & Bartlettlikely to Learning,be affected, time LLC trends, geographic trends, and© Jonesother variables & Bartlett that affect Learning, LLC NOT FOR SALEthe distributionOR DISTRIBUTION of TSS. A second example is myocardialNOT infarctionFOR SALE (MI; heartOR DISTRIBUTION attack). A clinical description of MI would list specific signs and symptoms, such as chest pain, heart rate, nausea, and other individual characteristics of the patient. The epidemiologic description of the same condition would indicate © Jones & Bartlett Learning,which LLC age groups would be most likely© Jones to be affected,& Bartlett seasonal Learning, trends in heartLLC NOT FOR SALE OR DISTRIBUTIONattack rates, geographic variations inNOT frequency, FOR andSALE other OR characteristics DISTRIBUTION of persons associated with the frequency of heart attack in populations. Referring again to the vignettes, one may note that the problem that plagued Kinfumu in Case 2 was recognized as a particularly acute problem for epidemi- ©ology Jones when &similar Bartlett complaints Learning, from other LLC patients were discovered and© the Jones dis- & Bartlett Learning, LLC NOTease began FOR to spread.SALE If OR more DISTRIBUTION than one person complains about a health NOTproblem, FOR SALE OR DISTRIBUTION the health provider may develop the suspicion that some widespread exposure rather than something unique to an individual is occurring. The clinical observation might suggest further epidemiologic investigation of the problem.

© Jones & BartlettHealth Learning, Phenomena LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION As indicated in the definition, epidemiology is used to investigate many different kinds of health outcomes. These range from infectious diseases to

12 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC chronic disease, and various states of health, such as disability, injury, limita- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION tion of activity, and mortality.17 Other health outcomes have included positive functioning of the individual and active life expectancy as well as health- related events, including mental disorders, suicide, substance abuse, and injury. Epidemiology’s concern with positive states of health is illustrated by © Jones & Bartlettresearch into Learning, active life expectancy LLC among geriatric populations.© Jones This & Bartlett research Learning, LLC NOT FOR SALEseeks to OR determine DISTRIBUTION the factors associated with optimalNOT mental FOR and SALE physical OR DISTRIBUTION functioning as well as enhanced quality of life and ultimately aims to limit disability in later life.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Morbidity and Mortality NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Two other terms central to epidemiology are morbidity and mortality. The for- mer, morbidity, designates illness, whereas the latter, mortality, refers to death. Note that most measures of morbidity and mortality are defined for specific types© Jonesof morbidity & Bartlett or causes ofLearning, death. LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Aims and Levels The preceding sections hinted at the complete scope of epidemiology. As the basic method of public health, epidemiology is concerned with efforts to © Jones & Bartlettdescribe, explain, Learning, predict, LLC and control. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION To describe the health status of populations means to enumerate the cases of disease, to obtain relative frequencies of the disease within subgroups, and to discover important trends in the occurrence of disease. To explain the etiology of disease means to discover causal factors as well as © Jones & Bartlett Learning,to LLC determine modes of transmission.© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION To predict the occurrence of diseaseNOT is FOR to estimate SALE the OR actual DISTRIBUTION number of cases that will develop as well as to identify the distribution within populations. Such information is crucial to planning interventions and allocation of healthcare resources. © JonesTo control &the Bartlett distribution Learning, of disease, LLC the epidemiologic approach is© used Jones & Bartlett Learning, LLC NOTto preventFOR SALE the occurrence OR DISTRIBUTION of new cases of disease, to eradicate existingNOT FOR SALE OR DISTRIBUTION cases, and to prolong the lives of those with the disease.

The implication of these aims is that epidemiology has two different goals. © Jones & BartlettOne is improved Learning, understanding LLC of the natural history of© diseaseJones and & the Bartlett factors Learning, LLC NOT FOR SALEthat influence OR DISTRIBUTION its distribution. With the knowledge thatNOT is obtained FOR SALEfrom such OR DISTRIBUTION efforts, one can then proceed to accomplish the second goal: intervention.

F OUNDATIONS OF E PIDEMIOLOGY 13

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTFoundations FOR SALE OR of DISTRIBUTION Epidemiology NOT FOR SALE OR DISTRIBUTION Epidemiology Is Interdisciplinary Epidemiology is an interdisciplinary field that draws from biostatistics and © Jones & Bartlettthe social Learning, and behavioral LLC sciences as well as from the© medically Jones related& Bartlett fields of Learning, LLC NOT FOR SALEtoxicology, OR DISTRIBUTION pathology, virology, genetics, microbiology,NOT and FOR clinical SALE medicine. OR DISTRIBUTION Terris18 pointed out that epidemiology is an extraordinarily rich and complex science that derives techniques and methodologies from many disciplines. He wrote that epidemiology “must draw upon and synthesize knowledge from the © Jones & Bartlett Learning,biological LLC sciences of man and of© his Jones parasites, & Bartlettfrom the numerousLearning, sciences LLC of the physical environment, and from the sciences concerned with human NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION society.”18(p. 203) To elaborate, some of the contributions of microbiology include information about specific disease agents, including their morphology and modes of transmission. The investigations of anthrax, Legionnaires’ disease, TSS, and infant © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC botulism (a condition linked to ingestion of spores, often found in honey, that NOTcause botulism)FOR SALE utilized OR microbiologic DISTRIBUTION techniques to identify possible infectiousNOT FOR SALE OR DISTRIBUTION agents. When the infectious agent is a virus, the expertise of a virologist may be required. Clinical medicine is involved in the diagnosis of the patient’s state of health, particularly when defining whether the patient has a specific disease or © Jones & Bartlettcondition. Learning, A pathologist’s LLC expertise may help differentiate© Jones between & Bartlettnormal and Learning, LLC NOT FOR SALEdiseased OR tissue.DISTRIBUTION From our previous examples, clinicalNOT medicine FOR diagnosed SALE OR the DISTRIBUTION individuals’ symptoms or signs of ill health. Astute physicians and nurses may suggest epidemiologic research on the basis of clinical observations. Toxicology is concerned with the presence and health effects of chemical agents, particularly © Jones & Bartlett Learning,those LLC found in the environment and© theJones workplace. & Bartlett Regarding Learning, hazardous waste LLC NOT FOR SALE OR DISTRIBUTIONsites, toxicologic knowledge helps NOTdetermine FOR the SALE presence OR of noxiousDISTRIBUTION chemical agents and whether the health effects observed are consistent with the known effects of exposure to toxic agents. When responses to exogenous agents vary from person to person, geneticists may become part of the team. Social and ©behavioral Jones sciences& Bartlett elucidate Learning, the role of LLC race, social class, education,© cultural Jones & Bartlett Learning, LLC NOTgroup FORmembership, SALE andOR behavioral DISTRIBUTION practices in health-related phenomena.NOT FOR SALE OR DISTRIBUTION Social and behavioral science disciplines, that is, sociology and psychology, are devoted respectively to the development of social theory and the study of behav- ior. The special concern of social epidemiologic approaches is the study of social 19 © Jones & Bartlettconditions Learning, and disease LLC processes. Furthermore, much© Jones of the methodology & Bartlett on Learning, LLC NOT FOR SALEsampling, OR DISTRIBUTION measurement, questionnaire development,NOT design, FOR and SALEdelivery, OR and DISTRIBUTION methods of group comparison are borrowed from the social sciences. Finally, the

14 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC field of biostatistics is critical to the evaluation of epidemiologic data, especially NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION when one is trying to separate chance from meaningful observations. Epidemiology profits from the interdisciplinary approach because the causality of a particular disease in a population may involve the interaction of multiple factors. The contributions of many disciplines help unravel the factors associated © Jones & Bartlettwith a particular Learning, disease. LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Methods and Procedures Population research is empirical and requires quantification of relevant factors. Quantification refers to the translation of qualitative impressions into numbers. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Qualitative sources of information about disease may be, in illustration, a physi- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION cian’s observations derived through medical practice about the types of people among whom a disease seems to be common. Epidemiologists enumerate cases of disease to objectify subjective impressions. Quantification is a central activity of epidemiology; the standard epidemiologic measures often require counting the© number Jones of & cases Bartlett of disease Learning, and examining LLC their distribution according© Jones to & Bartlett Learning, LLC demographicNOT FOR variables, SALE such OR as DISTRIBUTION age, sex, race, and other variables, such asNOT expo- FOR SALE OR DISTRIBUTION sure category and clinical features. The following quotation illustrates a summary of the characteristics of 51 suspected cases of severe acute respiratory syndrome (SARS) that were reported to the CDC as of early 2003: © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The Language of Quantification Severe Acute Respiratory Syndrome (SARS) in the United States © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION As of March 26, [2003] CDC has received 51 reports of suspected SARS cases from 21 states . . . identified using the CDC updated interim case definition [refer to Table 1–1] . . . The first suspected case was identi- ©fied Jones on March & Bartlett 15, in a manLearning, aged 53 yearsLLC who traveled to Singapore© Jones & Bartlett Learning, LLC NOTand became FOR illSALE on March OR 10. DISTRIBUTION Four clusters of suspected cases have beenNOT FOR SALE OR DISTRIBUTION identified, three of which involved a traveler who had visited Southeast Asia (including Guangdong province, Hong Kong, or Vietnam) and a single family contact. One of these clusters involved suspected cases in © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR continuesSALE OR DISTRIBUTION

F OUNDATIONS OF E PIDEMIOLOGY 15 (4) (2) (10) (27) (%) (49) (51) 42 yrs (3/25/03-P) § § 8 mos–78 yrs United States 2 § 0§ N (%) © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 53 yrs Taiwan 25–64 yrs (3/25/03-S) 2 (33) 5 § 0 N DISTRIBUTION. (%) © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION OR © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 38 yrs SALE 1–49 yrs Thailand (3/23/03-S/P) 3 (75) 6 (100) 14 § 0 N FOR NOT © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION (9)(3) 1 0 (25) 2 (33) 1 § LLC. (%) 38 yrs Vietnam Learning, 18–66 yrs (3/24/03-P) 5 22 (37) 3 (75) 3 (50) 25 37 (63) 1 (25) 3 (50) 26 N 37 (63) 1 (25) 0 59 (100) 4 (100) 6 (100) 51§ (100) NA Bartlett & § Jones (4)§ 2 ** NA†† (%) (46) § (99) § © (100)§ 59 (100) 4 (100) 6 (100) 20§ (39) NA NA 50% 50% © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Hong Kong (3/25/03-S/P) N 10 § NA 156 § 286 § 290§ (100) Exposure Category, Clinical Features, and Demographics of Reported Severe Acute Respiratory Syndrome (SARS) © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Modified from Centers for Disease Control and Prevention. Update: Outbreak of severe acute respiratory syndrome—worldwide, 2003. MMWR. Male Female Healthcare worker 134 § Ever hospitalizedPneumonia 290 § Close contact¶ Sex §§ Age, median Ever ventilated Age, range Dead Abbreviation: N, number. * Locations used different SARS case definitions. unknown. probable case; U, †S, suspected case; P, § resident (Patient B) was hospitalized One U.S. in Vietnam and died Hong Kong before he could return to the United States. He is counted as a Hong Kong case. ¶ lived with, or had direct Person contact having cared with respiratory for, secretions and body fluids of a person with SARS. ** Of the 290 SARS patients in Hong Kong, most of remaining 156 patients are believed to be close contacts. †† Not available. §§ Only percentages were reported for sex data. Source: 2003;52:244. Category Table 1–1 Table Cases* in Selected Locations, 2003 Total cases† Total Exposure (As of date) Clinical features Demographics © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 51618_CH01_FRIIS.qxd 2/20/08 12:14 PM Page 16

16 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION patients L and M . . . who had stayed together at hotel M during March 1–6, when other hotel guests were symptomatic. Patient L became sick on March 13 after returning to the United States. His wife, patient M, became ill several days after the onset of her husband’s symptoms, sug- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC gesting secondary transmission. Three patients in the United States with NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION suspected SARS (patients I, L, and M) reported staying at hotel M when other persons staying in the hotel were symptomatic. The fourth cluster began with a suspected case in a person who traveled in Guangdong province and Hong Kong. Two [health care workers] subsequently © Jones & Bartlett Learning,became LLC ill at the U.S. hospital where© Jones this patient & Bartlett was admitted. Learning,20(p. 244) LLC NOT FOR SALE OR DISTRIBUTIONSince 2005, no additional SARS casesNOT have FOR been SALE reported. OR DISTRIBUTION

Epidemiologists sometimes present quantified information as graphs and tables© Jones that illustrate & Bartlett pictorially Learning, the frequency LLC of disease. Quantification enables© Jones & Bartlett Learning, LLC theNOT epidemiologist FOR SALE to investigate OR DISTRIBUTION the sources of variation of a disease byNOT time, FOR SALE OR DISTRIBUTION place, and person: When did the case occur? Where was it located? Who was affected? We offer many examples of quantification throughout this text. Table 1–1 © Jones & Bartlettreports the Learning,characteristics LLC of SARS cases in selected locations© Jones in 2003. & Bartlett Learning, LLC NOT FOR SALEOther OR key DISTRIBUTION methods for the graphic presentation ofNOT data areFOR the SALEuse of pie OR DISTRIBUTION charts, bar charts, and line graphs. Figure 1–3 shows an example of each type: a pie chart (A, fatal occupational injuries in the United States); a bar chart (B, firearm injury death rates); and a line graph (C, motor vehicle traffic death rates). © Jones & Bartlett Learning,Epidemiologists LLC use these types of graphs© Jones to describe & characteristicsBartlett Learning, of data, such LLC 21 NOT FOR SALE OR DISTRIBUTIONas subgroup differences and time trends.NOT FOR SALE OR DISTRIBUTION Use of Special Vocabulary Epidemiology employs a unique vocabulary of terms to describe the frequency of occurrence© Jones of disease. & Bartlett These termsLearning, are presented LLC in Chapters 3 and 4. A different© Jones & Bartlett Learning, LLC collectionNOT FOR of terms SALE is used OR in reference DISTRIBUTION to the array of study designs availableNOT to FOR SALE OR DISTRIBUTION epidemiologists. Chapters 6, 7, and 8 define and characterize these study approaches. Finally, special terms have been developed to convey the results and to aid in the interpretation of epidemiologic investigations. These are defined © Jones & Bartlettand illustrated Learning, in Chapter LLC 10. © Jones & Bartlett Learning, LLC NOT FOR SALEDorland’s OR DISTRIBUTIONIllustrated Medical Dictionary defines the wordNOT epidemic FOR SALEas “attack- OR DISTRIBUTION ing many people at the same time, widely diffused and rapidly spreading.” More

F OUNDATIONS OF E PIDEMIOLOGY 17

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC AA Other events and exposures 0.4% Fires and explosions 3% NOT FOR SALE OR DISTRIBUTIONExposure to harmful substances NOT FOR SALE OR DISTRIBUTION or environments 10%

Falls Transportation 10% incidents 41% © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Contact with objects NOT FOR SALE OR DISTRIBUTION and equipmentNOT 15%FOR SALE OR DISTRIBUTION

Assaults and violent acts 20%

B © Jones & Bartlett Learning, LLC United States © Jones & Bartlett Learning, LLC Norway NOT FOR SALE OR DISTRIBUTION Israel NOT FOR SALE OR DISTRIBUTION Canada New Zealand Australia France Denmark © Jones & BartlettSweden Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEScotland OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The Netherlands England and Wales

0 5 101520253035404550556065 Deaths per 100,000 population © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEC OR DISTRIBUTION35 NOT FOR SALE OR DISTRIBUTION All motor vehicle traffic 25

Blood alcohol concentration .01 and over 15 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC

NOT FOR SALE OR DISTRIBUTION 10 Blood alcohol concentration 0.00NOT FOR SALE OR DISTRIBUTION

7 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 FIGURE 1–3 Examples of three different presentations of epidemiologic ©data. Jones (A) Pie & chart.Bartlett Percentage Learning, distribution LLC of fatal occupational injuries,© Jones & Bartlett Learning, LLC NOTaccording FOR to SALEthe event: OR United DISTRIBUTION States, 1994–1995. (B) Bar graph. NOTFirearm FOR SALE OR DISTRIBUTION injury death rates among males 15 to 24 years of age for selected countries and selected years (1992–1995). (C) Line graph. Motor vehicle traffic death rates by alcohol involvement among persons 1 to 34 years of age in the United States during 1985–1995. Source: Reprinted from Fingerhut © Jones & BartlettLA, Warner Learning, M. Injury LLC Chartbook. Health, United States,© Jones 1996–97 &. NationalBartlett Learning, LLC NOT FOR SALECenter OR for DISTRIBUTION Health Statistics; 1997. NOT FOR SALE OR DISTRIBUTION

18 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC precisely, an epidemic refers to an excessive occurrence of a disease: “Most cur- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION rent definitions [of epidemic] stress the concept of excessive prevalence as its basic implication in both lay and professional usage.”22(p. 2) The following passage illustrates this notion by defining an epidemic as:

© Jones & BartlettThe occurrence Learning, in a community LLC or region of cases of an ©illness Jones (or an &outbreak) Bartlett Learning, LLC NOT FOR SALEclearly OR in excess DISTRIBUTION of expectancy. The number of cases indicatingNOT presence FOR of SALE an epi- OR DISTRIBUTION demic will vary according to the infectious agent, size and type of population exposed, previous experience or lack of exposure to the disease, and time and place of occurrence; epidemicity is thus relative to usual frequency of the disease in the same area, among the specified population, at the same season of the year. A single © Jones & Bartlett Learning,case ofLLC a communicable disease long absent© Jones from a population & Bartlett or the Learning, first invasion LLC NOT FOR SALE OR DISTRIBUTIONby a disease not previously recognized inNOT that area FOR requires SALE immediate OR reporting DISTRIBUTION and epidemiologic investigation; two cases of such a disease associated in time and place are sufficient evidence of transmission to be considered an epidemic.23(pp. 569–570)

In current thinking, an epidemic is not confined to infectious diseases. Take, for example,© Jones the Love & Bartlett Canal incident Learning, that generated LLC spirited public debate and© media Jones & Bartlett Learning, LLC attentionNOT FORduring SALEthe late 1970s.OR DISTRIBUTION Love Canal was a toxic waste disposal site locatedNOT FOR SALE OR DISTRIBUTION in Niagara Falls, New York. It was the location for burial of thousands of chemical- filled drums deposited by the Hooker Chemicals & Plastics Corporation. Eventually, the waste disposal site was covered and converted into a housing tract. © Jones & BartlettSubsequently, Learning, residents of LLCthe area reported several different© Jonestypes of health & Bartlett effects, Learning, LLC NOT FOR SALEincluding OR miscarriages, DISTRIBUTION birth defects, and mental retardation.NOT The FOR Love SALE Canal site OR DISTRIBUTION was the focus of extensive health effects studies and epidemiologic research. By referring to the case studies reported in this text, you have seen additional examples—red spots among airline FAs and TSS—that illustrate two instances © Jones & Bartlett Learning,in which LLC epidemiologic methodology© wasJones employed & Bartlett to study Learning, noninfectious LLC NOT FOR SALE OR DISTRIBUTIONconditions. TSS and red spots among NOTairline FORFAs both SALE represented OR DISTRIBUTION apparent epidemics because the usual or expected rate was nil. Epidemiologic methods also are used to investigate occupationally associated illness (e.g., brown lung disease among textile workers and asbestosis among shipyard workers), environmental health© Jones hazards &(e.g., Bartlett toxic chemicals Learning, and air LLC pollution), and conditions associ-© Jones & Bartlett Learning, LLC atedNOT with FOR lifestyle SALE (e.g., accidents,OR DISTRIBUTION ischemic heart disease, and certain formsNOT of FOR SALE OR DISTRIBUTION cancer). Related to the term epidemic is the term pandemic, which refers to an epidemic on a worldwide scale; during a pandemic, large numbers of persons may © Jones & Bartlettbe affected Learning, and a disease LLCmay cross international borders.© ExamplesJones & are Bartlett flu pan- Learning, LLC NOT FOR SALEdemics, OR such DISTRIBUTION as the pandemic of 1918 and more recent NOTflu pandemics FOR SALEthat occur OR DISTRIBUTION periodically. The term endemic is used to characterize a disease that is habitually present in a particular geographical region. To illustrate, malaria is endemic in

F OUNDATIONS OF E PIDEMIOLOGY 19

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC some tropical areas of Asia, and cholera is endemic to less developed countries NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION where sanitation is lacking. Previously, during the 19th century, cholera was endemic to Western countries, such as England and the United States. However, cholera is no longer endemic to these two countries because of the introduction of sanitation and other public health measures. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEMethods OR DISTRIBUTION for Ascertainment of Epidemic FrequencyNOT FOR of SALE Disease OR DISTRIBUTION The CDC and vital statistics departments of state and local governments collect surveillance data on a continuing basis to determine whether an epidemic is tak- ing place. The word surveillance denotes the systematic collection of data pertain- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC ing to the occurrence of specific diseases, the analysis and interpretation of these NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION data, and the dissemination of consolidated and processed information to con- tributors to the surveillance program and other interested persons. For example, if 500 heart attack deaths are reported in an upstate New York community during a particular year, this information by itself would be insufficient to justify the asser- ©tion Jones that an &epidemic Bartlett of heart Learning, attacks has LLC occurred. The usual frequency© of Jones heart & Bartlett Learning, LLC NOTattacks FOR would SALE need to beOR determined DISTRIBUTION in the same community at some priorNOT time, FOR SALE OR DISTRIBUTION and the size, age, and sex distribution of the population would need to be known. A second example is shown in Figure 1–4 for influenza and pneumonia deaths.

Epidemic 10 Threshhold

Percentage of all deaths 6 Seasonal Baseline © Jones2003 & Bartlett Learning,2004 LLC2005 2006 © Jones & Bartlett Learning, LLC 4 NOT20 FOR 30 40SALE 50 10 OR 20 30DISTRIBUTION 40 50 10 20 30 40 50 10 20 30 40NOT 201050 FOR SALE OR DISTRIBUTION Weeks FIGURE 1–4 Pneumonia and influenza mortality for 122 U.S. cities, week ending May 19, 2007. Source: From Centers for Disease Control and © Jones & BartlettPrevention. Learning, Influenza LLC (Flu) Weekly Report: Influenza© Jones Summary & Bartlett Update Learning, LLC Week ending May 19, 2007–Week 20. Available at: http://www.cdc.gov/ NOT FOR SALEflu/weekly/weeklyarchives2006–2007/weekly20.htm. OR DISTRIBUTION NOT Accessed FOR October SALE 11, OR DISTRIBUTION 2007.

20 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Figure 1–4 exhibits weekly pneumonia and influenza deaths in the United NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION States from winter 2003 to spring 2007. It demonstrates that influenza has an underlying seasonal baseline, reflected in its cyclic seasonal increases and declines in mortality. The lower line denotes the usual number of total deaths to be expected from pneumonia and influenza during each week of the year. An upper © Jones & Bartlettparallel line Learning, indicates the LLCfrequency of disease at the epidemic© Jones threshold, & Bartlett that is, Learning, LLC NOT FOR SALEthe minimum OR DISTRIBUTION number of deaths that would support theNOT conclusion FOR that SALE an epi- OR DISTRIBUTION demic was underway. Figure 1–4 demonstrates that the combined pneumonia and influenza deaths exceeded the epidemic threshold during the 2003–2004 and 2004–2005 flu seasons. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Historical Antecedents of Epidemiology

To put the discipline in proper perspective, we now outline some of the historical trends that led to the development of epidemiology or were historically significant© Jones for the & field. Bartlett It may Learning,be said that epidemiology LLC began with the Greeks,© Jones & Bartlett Learning, LLC whoNOT in their FOR concern SALE for theOR ancient DISTRIBUTION epidemics and deadly toll of diseases, NOTattrib- FOR SALE OR DISTRIBUTION uted disease causality to environmental factors. Early causal explanations for epidemics included the wrath of the gods, the breakdown of religious beliefs and morality, the influence of weather, and “bad air.” During the medieval period, © Jones & Bartlettthe Black Death Learning, caused by LLC plague killed more than 25%© of Jones the European & Bartlett popu- Learning, LLC NOT FOR SALElation. AnotherOR DISTRIBUTION terrible scourge was smallpox: Edward NOTJenner’s FOR work SALEled to the OR DISTRIBUTION development of an effective vaccination against smallpox. During the late Renaissance, pioneering biostatisticians quantified morbidity and mortality trends. Often cited as another major development is John Snow’s investigations © Jones & Bartlett Learning,of London LLC cholera outbreaks, reported© in Jones Snow on &Cholera Bartlett.24 A contemporary Learning, ofLLC NOT FOR SALE OR DISTRIBUTIONSnow, William Farr, promoted innovativeNOT uses FOR of vital SALE statistics OR data. DISTRIBUTION During the 19th century, early microbiologists formalized the germ theory of disease, which attributed diseases to specific organisms. At the beginning of the 20th century, a flu pandemic killed more than 50 million people worldwide. Each of these historical© Jones developments & Bartlett that contributed Learning, to the LLC genesis of epidemiology is discussed© Jones & Bartlett Learning, LLC in NOTturn below. FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Environment as a Factor in Disease Causation The following account of a deadly disease by Thucydides records, in detail, the 25 © Jones & Bartlettravages produced Learning, by “Thucydides’ LLC plague” ; such graphic© Jones descriptions & Bartlett of major Learning, LLC NOT FOR SALEepidemics OR in DISTRIBUTION history indicate this early author’s concernNOT with FOR the causality SALE ofOR DISTRIBUTION these remarkable phenomena:

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 21

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Many who were in perfect health, all in a moment, and without apparent reason, NOTwere FOR seized SALEwith violent OR heats DISTRIBUTION in the head and with redness and inflammationNOT of FOR SALE OR DISTRIBUTION the eyes. Internally the throat and the tongue were quickly suffused with blood, and the breath became unnatural and fetid. There followed sneezing and a hoarse- ness; in a short time the disorder, accompanied by a violent cough, reached the © Jones & Bartlettchest; Learning,then fastening lowerLLC down, it would move the stomach© Jones and bring & Bartletton all the Learning, LLC vomits of bile to which physicians have ever given names; and they were very dis- NOT FOR SALEtressing. OR DISTRIBUTION An ineffectual retching producing violent convulsionsNOT FOR attacked SALE most ofOR DISTRIBUTION the sufferers; some as soon as the previous symptoms had abated, others not until long afterwards. The body externally was not so very hot to the touch, nor yet pale; it was of a livid color inclining to red, and breaking out in pustules and ulcers. But © Jones & Bartlett Learning,the LLC internal fever was intense; the sufferers© Jones could & not Bartlett bear to have Learning, on them even LLC the finest linen garment; they insisted on being naked, and there was nothing NOT FOR SALE OR DISTRIBUTIONwhich they longed for more eagerlyNOT than to FOR throw SALEthemselves OR into DISTRIBUTION cold water . . . While the disease was at its height, the body, instead of wasting away, held out amid these sufferings in a marvelous manner, and either they died on the seventh or ninth day, not of weakness, for their strength was not exhausted, but of internal © Jonesfever, which & wasBartlett the end Learning,of most; or, if theyLLC survived, then the disease descended© Jones & Bartlett Learning, LLC into the bowels and there produced violent ulceration; severe diarrhea at the same NOTtime FOR set in, SALEand at a laterOR stage DISTRIBUTION caused exhaustion, which finally with a fewNOT excep- FOR SALE OR DISTRIBUTION tions carried them off.25(p. 21)

Hippocrates, in On Airs, Waters, and Places,26 gave birth in about 400 BC to © Jones & Bartlettthe idea Learning, that disease mightLLC be associated with the ©physical Jones environment; & Bartlett his Learning, LLC NOT FOR SALEthinking OR representedDISTRIBUTION a movement away from supernaturalNOT FORexplanations SALE of OR dis- DISTRIBUTION ease causation to a rational account of the origin of humankind’s illnesses. Note in the following passage his reference to climate and physical environment:

Whoever wishes to investigate medicine properly should proceed thus: in the first © Jones & Bartlett Learning,place LLC to consider the seasons of the© year, Jones and what & effectsBartlett each ofLearning, them produces LLC NOT FOR SALE OR DISTRIBUTION(for they are not at all alike, but differNOT much FOR from SALE themselves OR in DISTRIBUTION regard to their changes). Then the winds, the hot and the cold, especially such as are common to all countries, and then such as are peculiar to each locality. We must also consider the qualities of the waters, for as they differ from one another in taste and weight, so also do they differ much in their qualities. In the same manner, when one comes © Jonesinto a city & to whichBartlett he is aLearning, stranger, he ought LLC to consider its situation, how it© lies Jones as & Bartlett Learning, LLC NOTto the FOR winds SALE and the ORrising DISTRIBUTIONof the sun; for its influence is not the same whetherNOT it FOR SALE OR DISTRIBUTION lies to the north or the south, to the rising or to the setting sun. These things one ought to consider most attentively, and concerning the waters which the inhabitants use, whether they be marshy and soft, or hard, and running from elevated and rocky situations, and then if saltish and unfit for cooking; and the ground, © Jones & Bartlettwhether Learning, it be naked LLC and deficient in water, or wooded© Jones and well &watered, Bartlett and Learning, LLC NOT FOR SALEwhether OR DISTRIBUTION it lies in a hollow, confined situation, or is NOTelevated FOR and cold; SALE and the OR DISTRIBUTION mode in which the inhabitants live, and what are their pursuits, whether they are

22 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC fond of drinking and eating to excess, and given to indolence, or are fond of exer- NOTcise and FOR labor, SALEand not given OR to DISTRIBUTION excess in eating and drinking.26(pp. 156–157) NOT FOR SALE OR DISTRIBUTION The Black Death Occurring between 1346 and 1352, the Black Death is a dramatic example of a © Jones & Bartlettpandemic ofLearning, great historical LLC significance to epidemiology.© 27JonesThe Black & BartlettDeath is Learning, LLC NOT FOR SALEnoteworthy OR becauseDISTRIBUTION of the scope of human mortality thatNOT it produced FOR SALE as well asOR DISTRIBUTION for its impact upon medieval civilization. Estimates suggest that the Black Death claimed about one-quarter to one-third of the population of Europe. Northern Africa and the near Middle East also were affected severely; at the inception of © Jones & Bartlett Learning,the outbreak, LLC the population of this region© Jones including & Bartlett Europe numbered Learning, about LLC NOT FOR SALE OR DISTRIBUTION100 million people; 20 to 30 million peopleNOT areFOR believed SALE to have OR died DISTRIBUTION in Europe. Historians attribute the Black Death to bubonic plague, which is the most common of the three forms of plague.28 The bacterium Yersinia pestis produces swelling of the lymph nodes in the groin and other sites of the body. These painful© Jones swellings, & Bartlettcalled buboes, Learning, are followed LLC in several days by high fever© Jonesand & Bartlett Learning, LLC theNOT appearance FOR of SALE black splotches OR DISTRIBUTION on the skin. The reservoir for Y. pestis is variousNOT FOR SALE OR DISTRIBUTION types of rodents, including rats. Plague can be transmitted when fleas that feed on rodents bite a human host. At the time of the Black Death, no method for treatment of plague existed. Most victims died within a few days after the occurrence of buboes. Currently, plague is treatable with antibiotics. In addition, © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC improvement in sanitary conditions has led to the decline in plague cases; 2,118 NOT FOR SALEcases were OR reported DISTRIBUTION worldwide in 2003. NOT FOR SALE OR DISTRIBUTION Use of Mortality Count In 1662, John Graunt published Natural and Political Observations Mentioned in © Jones & Bartlett Learning,a Following LLC Index, and Made Upon the© BillsJones of Mortality & Bartlett.29 This Learning, work recorded LLC NOT FOR SALE OR DISTRIBUTIONdescriptive characteristics of birth andNOT death FORdata, including SALE ORseasonal DISTRIBUTION variations, infant mortality, and excess male over female differences in mortality. Graunt’s work made a fundamental contribution by discovering regularities in medical and social phenomena. He is said to be the first to employ quantitative methods in ©describing Jones population & Bartlett vital Learning, statistics by organizing LLC mortality data in a mortal-© Jones & Bartlett Learning, LLC ityNOT table andFOR has SALE been referred OR DISTRIBUTIONto as the Columbus of statistics. Graunt’s NOTproce- FOR SALE OR DISTRIBUTION dures allowed the discovery of trends in births and deaths due to specific causes. Although his conclusions were sometimes erroneous, his development of statistical methods was highly important.30 © Jones & BartlettConcerning Learning, sex differences LLC in death rates, Graunt wrote:© Jones & Bartlett Learning, LLC NOT FOR SALEOf the OR difference DISTRIBUTION between the numbers of Males and FemalesNOT. The next FOR Observation SALE OR DISTRIBUTION is, That there be more Males than Females . . . There have been Buried from the

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 23

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC year 1628, to the year 1662, exclusive, 209436 Males, and but 190474 Females: but NOTit will FOR be objected, SALE That OR in DISTRIBUTION London it may be indeed so, though otherwiseNOT else- FOR SALE OR DISTRIBUTION where; because London is the great Stage and Shop of business, wherein the Masculine Sex bears the greatest part. But we Answer, That there have been also Christened within the same time 139782 Males, and but 130866 Females, and that © Jones & Bartlettthe Country-Accounts Learning, LLC are consonant enough to those© Jones of London & uponBartlett this Learning, LLC matter.29(p. 44) NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Figure 1–5 shows the 10 leading causes of mortality from the Yearly Mortality Bill for 1632.

© Jones & Bartlett Learning,Edward LLC Jenner and Smallpox© VaccinationJones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONThe term vaccination derives from NOTthe Latin FOR word SALE for cow OR (vacca), DISTRIBUTION the source of the cowpox virus that was used to create a vaccine against smallpox. A precursor of smallpox vaccination was variolation, which referred to an early Asian method of conferring immunity to smallpox by introducing dried scabs from smallpox ©patients Jones into & the Bartlett noses of potentialLearning, victims LLC who wished to be protected ©from Jones this & Bartlett Learning, LLC NOTdisease. FOR31 Variolation SALE oftenOR DISTRIBUTIONproduced a milder case of disease with a muchNOT lower FOR SALE OR DISTRIBUTION fatality rate than that caused by community-acquired smallpox. The method

Fever

Collick, Stone, and Strangury © Jones & Bartlett Learning, LLC Flox and Small Pox © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONBloody Flux, Scowring, and Flux NOT FOR SALE OR DISTRIBUTION Dropsie and Swelling

Convulsion

Childbed © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALELiver grown OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 0 500 1000 1500 2000 2500 Number of deaths FIGURE 1–5 Yearly Mortality Bill for 1632: The 10 leading causes of © Jones & Bartlettmortality Learning, in Graunt’s LLC Time. Source: Data from Graunt© Jones J. Natural & Bartlett and Learning, LLC Political Observations, Mentioned in a Following Index, and Made upon the NOT FOR SALEBills OR of Mortality DISTRIBUTION, 2nd ed. London: Tho. Roycroft;NOT 1662: FOR p. 8. SALE OR DISTRIBUTION

24 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC gained popularity in Europe during the early 1700s, when the procedure was NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION modified by injecting infectious material under the skin; variolation was first tested among abandoned children and prisoners. When it was declared safe, members of the English royal family were inoculated. Edward Jenner (Figure 1–6) is credited with the development of the smallpox © Jones & Bartlettvaccination, Learning, a lower-risk methodLLC for conferring immunity© againstJones smallpox & Bartlett than Learning, LLC NOT FOR SALEvariolation. OR32 DISTRIBUTIONHe was fascinated by folk wisdom, whichNOT suggested FOR thatSALE dairy- OR DISTRIBUTION maids who had contracted cowpox seemed to be immune to smallpox. Infection with the cowpox virus produced a much less severe form of disease than smallpox. Jenner conducted an experiment in which he used scabs from the cowpox © Jones & Bartlett Learning,lesions onLLC the arm of a dairy maid, Sarah© JonesNelmes (Figure& Bartlett 1–7), to Learning, create a small- LLC NOT FOR SALE OR DISTRIBUTIONpox vaccine. He then used the materialNOT to vaccinate FOR anSALE eight-year-old OR DISTRIBUTION boy, James

FIGURE 1–6 Edward Jenner. Source: From the National Library of © Jones & BartlettMedicine. Learning,Smallpox: A LLCgreat and terrible scourge: Vaccination.© Jones &Available Bartlett Learning, LLC at: http://www.nlm.nih.gov/exhibition/smallpox/sp_vaccination.html. NOT FOR SALEAccessed OR October DISTRIBUTION 11, 2007. NOT FOR SALE OR DISTRIBUTION

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 25

FIGURE 1–7 Arm of Sarah Nelmes with lesions of cowpox. Source: From the National Library of Medicine. Smallpox: A great and terrible © Jones & Bartlettscourge: Learning, Vaccination. LLC Available at: http://www.nlm.nih.gov/exhibition/© Jones & Bartlett Learning, LLC NOT FOR SALEsmallpox/sp_vaccination.html. OR DISTRIBUTION Accessed October NOT11, 2007. FOR SALE OR DISTRIBUTION

Phipps. Following the vaccination, Phipps appeared to develop immunity to the © Jones & Bartlett Learning,smallpox LLC virus to which he was re-exposed© Jones several & Bartlett times subsequently. Learning, Later, LLC NOT FOR SALE OR DISTRIBUTIONJenner vaccinated his own son and NOTseveral FORother children, SALE obtainingOR DISTRIBUTION similar positive findings, which were published in 1798. (In 1978, smallpox was finally eliminated worldwide; as of 1972, routine vaccination of the nonmilitary population of the United States was discontinued.)33 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Use of Natural Experiments NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Snow investigated a cholera epidemic that occurred during the mid-19th century in Broad Street, Golden Square, London. Snow’s work, a classic study that linked the cholera epidemic to contaminated water supplies, is noteworthy because it © Jones & Bartlettutilized Learning,many of the featuresLLC of epidemiologic inquiry:© Jones a spot map & Bartlettof cases and Learning, LLC NOT FOR SALEtabulation OR DISTRIBUTION of fatal attacks and deaths. Through the applicationNOT FOR of hisSALE keen pow-OR DISTRIBUTION ers of observation and inference, he developed the hypothesis that contaminated

26 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC water might be associated with outbreaks of cholera. He made several observa- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION tions that others had not previously made. One observation was that cholera was associated with water from one of two water supplies that served the Golden Square district of London.34 Broad Street was served by two separate water companies, the Lambeth Company and the Southwark and Vauxhall Company. © Jones & BartlettLilienfeld and Learning, Lilienfeld35 LLCwrote: © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION In London, several water companies were responsible for supplying water to different parts of the city. In 1849, Snow noted that the cholera rates were particularly high in those areas of London that were supplied by the Lambeth Company and the Southwark and Vauxhall Company, both of whom obtained their water from © Jones & Bartlett Learning,the Thames LLC River at a point heavily polluted© Jones with sewage. & Bartlett35(p. 36) Learning, LLC NOT FOR SALE OR DISTRIBUTIONSnow’s account of the outbreak of 1849NOT is FORfound SALEin Exhibit OR 1–2. DISTRIBUTION Between 1849 and 1854 the Lambeth Company had its source of water relo- cated to a less contaminated part of the Thames. In 1854, another epidemic of cholera occurred. This epidemic was in an area that consisted of two-thirds of London’s© Jones resident & Bartlettpopulation Learning, south of the Thames LLC and was being served by© both Jones & Bartlett Learning, LLC companies.NOT FOR In this SALE area, theOR two DISTRIBUTION companies had their water mains laid outNOT in an FOR SALE OR DISTRIBUTION interpenetrating manner, so that houses on the same street were receiving their water from different sources.35 This was a naturally occurring situation, a “natural experiment,” if you will, © Jones & Bartlettbecause in Learning,1849 all residents LLC received contaminated water© Jones from the & twoBartlett water Learning, LLC NOT FOR SALEcompanies. OR AfterDISTRIBUTION 1849, the Lambeth Company used lessNOT contaminated FOR SALE water byOR DISTRIBUTION relocating its water supply. Snow demonstrated that a disproportionate number of residents who contracted cholera in the 1854 outbreak used water from one water company, which received polluted water, in comparison with the other © Jones & Bartlett Learning,company, LLC which used relatively unpolluted© Jones water. & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONSnow’s methodology maintains contemporaryNOT FOR relevance. SALE His OR methods DISTRIBUTION utilized logical organization of observations, a natural experiment, and a quantitative approach.35 All these methods are hallmarks of present-day epidemiologic inquiry. Note that it is possible to visit the site of the pump that figured so prominently© Jones in & Snow’s Bartlett investigation Learning, of cholera; LLC a London public house on© Jonesthe & Bartlett Learning, LLC originalNOT site FOR of the SALE pump hasOR been DISTRIBUTION named in Snow’s honor. A replica of theNOT pump FOR SALE OR DISTRIBUTION is located nearby. Refer to Exhibit 1–3 for pictures and a reproduction of the text on the base of the replica. Another study, occurring during the mid-19th century, also used nascent epi- 36 © Jones & Bartlettdemiologic Learning, methods. Ignaz LLC Semmelweis, in his position© asJones a clinical & assistant Bartlett in Learning, LLC NOT FOR SALEobstetrics OR and DISTRIBUTION gynecology at a Vienna hospital, observedNOT that FOR women SALE in the OR DISTRIBUTION maternity wards were dying at high rates from puerperal fever. In 1840, when the

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 27

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC medical education system changed, he found a much higher mortality rate NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION among the women on the teaching wards for medical students and physicians than on the teaching wards for midwives. He postulated that medical students and physicians had contaminated their hands during autopsies. As a result, they transmitted infections while attending women in the maternity wards.37 When © Jones & Bartlettthe practice Learning, of hand washingLLC with chlorinated solutions© Jones was introduced, & Bartlett the Learning, LLC NOT FOR SALEdeath OR rate DISTRIBUTION for puerperal fever in the wards for medicalNOT students FOR and SALE physicians OR DISTRIBUTION dropped to a rate equal to that in the wards for midwives.

The most terrible outbreak of cholera which ever occurred in this kingdom, is probably that which took place in Broad Street, Golden © JonesSquare, & Bartlett and the adjoiningLearning, streets, LLC a few weeks ago. Within two© hun-Jones & Bartlett Learning, LLC NOT FORdred SALE and fifty OR yards DISTRIBUTION of the spot where Cambridge Street joinsNOT Broad FOR SALE OR DISTRIBUTION EXHIBIT 1–2 Street, there were upwards of five hundred fatal attacks of cholera in ten days. The mortality in this limited area probably equals any that was ever caused in this country, even by the plague; and it was much more © Jones & Bartlettsudden, Learning, as the greater LLC number of cases terminated© in Jonesa few hours. & Bartlett The mor- Learning, LLC NOT FOR SALEtality OR would DISTRIBUTION undoubtedly have been much greaterNOT had itFOR not been SALE for theOR DISTRIBUTION flight of the population. Persons in furnished lodgings left first, then other lodgers went away, leaving their furniture to be sent for when they could meet with a place to put it in. Many houses were closed altogether, owing to the death of the proprietors; and, in a great number of instances, the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC tradesmen who remained had sent away their families: so that in less than NOT FOR SALE OR DISTRIBUTIONsix days from the commencementNOT of the FOR outbreak, SALE the most OR afflictedDISTRIBUTION streets were deserted by more than three-quarters of their inhabitants. There were a few cases of cholera in the neighbourhood of Broad Street, Golden Square, in the latter part of August; and the so-called outbreak, © whichJones commenced & Bartlett in Learning,the night between LLC the 31st August and the© Jones 1st & Bartlett Learning, LLC NOTSeptember, FOR SALE was, as ORin all DISTRIBUTION similar instances, only a violent increaseNOT of the FOR SALE OR DISTRIBUTION malady. As soon as I became acquainted with the situation and extent of this irruption of cholera, I suspected some contamination of the water of the much-frequented street-pump in Broad Street, near the end of © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALEcontinues OR DISTRIBUTION

28 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC EXHIBITNOT FOR 1–2 SALEcontinued OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cambridge Street; but on examining the water, on the evening of the 3rd September, I found so little impurity in it of an organic nature, that I hesi- tated to come to a conclusion. Further inquiry, however, showed me that © Jones & Bartlettthere was Learning, no other circumstance LLC or agent common© to Jones the circumscribed & Bartlett Learning, LLC NOT FOR SALElocality OR in whichDISTRIBUTION this sudden increase of cholera occurred,NOT and FOR not SALEextend- OR DISTRIBUTION ing beyond it, except the water of the above mentioned pump. I found, moreover, that the water varied, during the next two days, in the amount of organic impurity, visible to the naked eye, on close inspection, in the © Jones & Bartlett Learning,form LLCof small white, flocculent particles;© Jones and I concluded& Bartlett that, Learning, at the com- LLC NOT FOR SALE OR DISTRIBUTIONmencement of the outbreak, it mightNOT possibly FOR have SALE been still OR more DISTRIBUTION impure. The deaths which occurred during this fatal outbreak of cholera are indicated in the accompanying map [Figure 1–8, see a copy of the complete map at the end of the book], as far as I could ascertain them . . . The dotted© Jones line on& Bartlettthe map surrounds Learning, the sub-districts LLC of Golden Square,© St. Jones & Bartlett Learning, LLC James’s,NOT FOR and BerwickSALE Street,OR DISTRIBUTION St. James’s, together with the adjoining NOTpor- FOR SALE OR DISTRIBUTION tion of the sub-district of St. Anne, Soho, extending from Wardour Street to Dean Street, and a small part of the sub-district of St. James’s Square enclosed by Marylebone Street, Titchfield Street, Great Windmill Street, © Jones & Bartlettand Brewer Learning, Street. All theLLC deaths from cholera which© were Jones registered & Bartlett in the Learning, LLC NOT FOR SALEsix weeks OR fromDISTRIBUTION 19th August to 30th September withinNOT this locality,FOR SALE as well OR DISTRIBUTION as those of persons removed into Middlesex Hospital, are shown in the map by a black line in the situation of the house in which it occurred, or in which the fatal attack was contracted . . . The pump in Broad Street is indicated on the map, as well as all the surrounding pumps to which the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC public had access at the time. It requires to be stated that the water of the NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION pump in Marlborough Street, at the end of Carnaby Street, was so impure that many people avoided using it. And I found that the persons who died near this pump in the beginning of September, had water from the Broad Street pump. With regard to the pump in Rupert Street, it will be noticed that© Jones some streets & Bartlett which are Learning, near to it on LLC the map, are in fact a good ©way Jones & Bartlett Learning, LLC removed,NOT FOR on accountSALE ORof the DISTRIBUTION circuitous road to it. These circumstancesNOT FOR SALE OR DISTRIBUTION being taken into account, it will be observed that the deaths either very much diminished, or ceased altogether at every point where it becomes decidedly nearer to send to another pump than to the one in Broad Street. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR continuesSALE OR DISTRIBUTION

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 29

FIGURE 1–8 Cholera deaths in the neighborhood of Broad Street, © Jones & BartlettAugust Learning,19 to September LLC 30, 1849. Source: Reprinted© Jones from Snow & Bartlett J. Snow Learning, LLC on Cholera, pp. 38–51, Harvard University Press © 1965. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

30 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY Legend Fatal Attacks Deaths © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION DISTRIBUTION. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION OR © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION SALE FOR p. 49, Harvard University Press, © 1965. Press, University 49, Harvard p. NOT Date © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION LLC. Learning, Bartlett & Jones © Aug. 31 Sept. 1 Sept. 2 Sept. 3 Sept. 4 Sept. 5 Sept. 6 Sept. 7 Sept. 8 © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Snow on Cholera, J. Snow Snow from Reprinted 0 80 60 40 20

160 140 120 100 Number 31– attacks and deaths, August district, London. Fatal Square in Golden The 1849 cholera outbreak © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION FIGURE 1–9 8. Source: September © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 51618_CH01_FRIIS.qxd 2/20/08 12:14 PM Page 31

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 31

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTEXHIBIT FOR 1–2 SALEcontinued OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION It may also be noticed that the deaths are most numerous near to the pump where the water could be more readily obtained . . . The greatest number of attacks in any one day occurred on the 1st of September, imme- © Jones & Bartlettdiately Learning, after the outbreak LLC commenced. The following© Jones day the & attacks Bartlett fell Learning, LLC NOT FOR SALEfrom OR one DISTRIBUTION hundred and forty-three to one hundredNOT and sixteen, FOR and SALE the day OR DISTRIBUTION afterwards to fifty-four . . . The fresh attacks continued to become less numerous every day. On September the 8th—the day when the handle of the pump was removed—there were twelve attacks; on the 9th, eleven; on © Jones & Bartlett Learning,the LLC 10th, five; on the 11th, five; ©on Jones the 12th, & only Bartlett one; and Learning, after this time, LLC NOT FOR SALE OR DISTRIBUTIONthere were never more than fourNOT attacks FOR on one SALE day. During OR DISTRIBUTION the decline of the epidemic the deaths were more numerous than the attacks, owing to the decrease of many persons who had lingered for several days in consec- utive fever [Figure 1–9]. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Source: Reprinted from Snow J. Snow on Cholera, p. 38–51, Harvard University Press, © 1965. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

William Farr A contemporary of John Snow, William Farr assumed the post of “Compiler of © Jones & BartlettAbstracts” Learning, at the General LLC Register Office (located in ©England) Jones in &1839 Bartlett and held Learning, LLC NOT FOR SALEthis ORposition DISTRIBUTION for 40 years. Among Farr’s contributionsNOT to public FOR health SALE and OR epi- DISTRIBUTION demiology was the development of a more sophisticated system for codifying medical conditions than was previously in use. Farr’s classification scheme, which departed from a narrow medical view, provided the foundation for the © Jones & Bartlett Learning,International LLC Classification of Diseases© Jones in use today. & Bartlett Also noteworthy Learning, is the LLC fact NOT FOR SALE OR DISTRIBUTIONthat Farr used data such as censusNOT reports FOR to study SALE occupational OR DISTRIBUTION mortality in England. In addition, he explored the possible linkage between mortality rates and population density, showing that both the average number of deaths and births per 1,000 living persons increased with population density (defined as number of per- ©sons Jones per square & Bartlett mile). Because Learning, of the excess LLC of births over deaths in all except© Jones the & Bartlett Learning, LLC NOTmost crowded FOR SALE areas, the OR population DISTRIBUTION tended to increase in the less crowdedNOT areas. FOR SALE OR DISTRIBUTION With respect to deaths in high mortality districts, such as Liverpool, which had a mortality rate more than 22 per 1,000 greater than that experienced in healthier districts, he attributed mortality to factors such as “. . . impurities of water, perni- © Jones & Bartlettcious dirts, Learning, floating dusts,LLC zynotic contagions, [and]© Jones crowdings & Bartlettin lodgings, Learning, LLC 38(p. 90) NOT FOR SALE...” OR DISTRIBUTIONThe healthier districts had “. . . a salubriousNOT soil, andFOR supply SALE the inhab- OR DISTRIBUTION itants with water generally free from organic impurities.”38(pp. 90–91)

32 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC IdentificationNOT FOR SALE of Specific OR DISTRIBUTION Agents of Disease NOT FOR SALE OR DISTRIBUTION In the late 1800s, Robert Koch verified that a human disease was caused by a specific living organism. His epoch-making study, Die Aetiologie der Tuberkulose, was published in 1882. This breakthrough made possible greater refinement of 39 © Jones & Bartlettthe classification Learning, of disease LLC by specific causal organisms.© Previously,Jones & the Bartlett group- Learning, LLC NOT FOR SALEing together OR DISTRIBUTIONof diseases according to grosser classificationsNOT had FOR hampered SALE their OR DISTRIBUTION epidemiologic study. King40 noted that Koch’s postulates are usually formatted as follows:

1. The microorganism must be observed in every case of the disease. © Jones & Bartlett Learning,2. ItLLC must be isolated and grown ©in pureJones culture. & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION3. The pure culture must, when inoculatedNOT FOR into SALE a susceptible OR animal,DISTRIBUTION repro- duce the disease. 4. The microorganism must be observed in, and recovered from, the exper- imentally diseased animal.40 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTKing noted,FOR “WhatSALE Koch OR accomplished, DISTRIBUTION in brief, was to demonstrate forNOT the FOR SALE OR DISTRIBUTION first time in any human disease a strict relation between a micro-organism and a disease.”40(p. 351) This specification of the causal disease organism provided a def- inite criterion for the identification of a disease, rather than the vague standards © Jones & BartlettKoch’s predecessors Learning, and contemporaries LLC had employed.© Jones & Bartlett Learning, LLC NOT FOR SALEIncreasing OR DISTRIBUTION awareness of the role of microbial agents inNOT the causation FOR SALE of human OR DISTRIBUTION illness—the germ theory of disease—eventually reached the public health community. One method to limit the spread of infectious disease was through the use of cartoons published in the popular media. Figure 1–10 suggested that skirts that trail on the ground (in fashion around the turn of the 20th century) could © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC bring deadly germs into the household.41 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The 1918 Influenza Pandemic So great was its impact, this outbreak has been referred to as “the Mother of All Pandemics.”© Jones42 &Also Bartlett known as Learning, the Spanish Flu,LLC the pandemic that occurred© dur-Jones & Bartlett Learning, LLC ingNOT the period FOR of SALE1918 to OR1919 DISTRIBUTIONkilled from 50 to 100 million persons worldwide.NOT FOR SALE OR DISTRIBUTION Estimates suggest that one-third of the world’s population of 1.5 billion at the time was infected and developed clinically observable illness. This very severe form of influenza had case-fatality rates of approximately 2.5% compared with © Jones & Bartlettthe 0.1% orLearning, lower rates observedLLC in other influenza pandemics.© Jones Differentiating & Bartlett Learning, LLC NOT FOR SALEthis form OR of DISTRIBUTION influenza from other outbreaks was its impactNOT onFOR healthy SALE young OR DISTRIBUTION

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 33

FIGURE 1–10 Samuel D. Ehrhart, “The Trailing Skirt: Death Loves a ©Shining Jones Mark,” & Bartlett Puck, August Learning, 8, 1900 LLC(original in color). Source: © Jones & Bartlett Learning, LLC NOTReprinted FOR with SALE permission OR DISTRIBUTION from Hansen B. The Image and AdvocacyNOT of FOR SALE OR DISTRIBUTION Public Health in American Caricature and Cartoons from 1860 to 1900, American Journal of Public Health, Vol 87, No 11, p. 1805, ©1997, American Public Health Association.

34 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT AFOR Visit SALE to theOR DISTRIBUTIONBroad Street Pump and theNOT FOR SALE OR DISTRIBUTION Sir John Snow Public House, Located at 39 Broadwick Street, London, England W1F9QJ © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION EXHIBIT 1–3

FIGURE 1–11 Photograph of John Snow.

© Jones & BartlettFigure 1–11 Learning, shows John LLC Snow. Figure 1–12 displays ©a replica Jones of the& Bartlett Broad Learning, LLC NOT FOR SALEStreet OR pump, DISTRIBUTION and Figure 1–13 presents a picture ofNOT the John FOR Snow SALE Pub. OR DISTRIBUTION Broad Street has been renamed Broadwick Street. The following section is reprinted from a plaque at the base of the replica. The plaque describes “The Soho Cholera Epidemic”: © Jones & Bartlett Learning,“Dr. LLC John Snow (1813–1858), a© noted Jones anaesthesiologist, & Bartlett livedLearning, near the LLC NOT FOR SALE OR DISTRIBUTIONfocus of the 1854 Soho cholera epidemic,NOT FORwhich centeredSALE ORon Broad DISTRIBUTION Street, as Broadwick Street was then called. In September of that year alone, over 500 people died in Soho from the disease. Snow had studied cholera in the 1848–49 epidemic in Southwark and Wandsworth. His theory that polluted drinking© Jones water & wasBartlett the [source] Learning, of transmission LLC of the disease [was] con-© Jones & Bartlett Learning, LLC firmedNOT FORwhen he SALE mapped OR cholera DISTRIBUTION deaths in Soho with the source of theNOT vic- FOR SALE OR DISTRIBUTION tims’ drinking water. He found that they were concentrated on the Broad Street public water pump. His theory initially met with some disbelief but such was his conviction that he had the pump handle removed to prevent © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALEcontinues OR DISTRIBUTION

H ISTORICAL A NTECEDENTS OF E PIDEMIOLOGY 35

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTEXHIBIT FOR 1–3 SALEcontinued OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION its further use. Soon afterwards the outbreak ended. The original pump is believed to have been situated outside the nearby ‘Sir John © Jones & BartlettSnow Learning,Public House.’” LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 1–12 Replica of Broad Street pump near its approximate original © location.Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 1–13 The John Snow Pub named in honor of the British © Jones & Bartlett Learning, LLC Anesthesiologist.© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

36 C HAPTER 1 HISTORY AND S COPE OF E PIDEMIOLOGY

adults;© Jones persons & aged Bartlett 20 to 40 Learning, accounted for LLC nearly half of the mortality ©toll Jones in & Bartlett Learning, LLC thisNOT pandemic, FOR whereas SALE influenza OR DISTRIBUTION deaths normally are more frequent amongNOT the FOR SALE OR DISTRIBUTION very young and the very old.43,44 The pandemic spread in three distinct waves during a one-year period throughout Europe, Asia, and North America; the first wave began in spring, 1918, with two subsequent waves occurring during the fall © Jones & Bartlettand winter Learning,of 1918 to 1919. LLC In the United States, the ©flu’s Jones impact was& Bartlett so great Learning, LLC NOT FOR SALEthat healthcare OR DISTRIBUTION facilities were taxed to the limit. As a resultNOT of FORlarge numbers SALE ofOR DISTRIBUTION deaths, the bodies of victims accumulated in morgues awaiting burial, which was delayed because of a shortage of coffins and morticians. A repeat of the 1918 pandemic is within the realm of possibility, raising ques- © Jones & Bartlett Learning,tions about LLC how modern society would© cope Jones with such& Bartlett an event. Learning,Will healthcare LLC NOT FOR SALE OR DISTRIBUTIONfacilities have adequate “surge” capacityNOT to deal FOR with SALE a sudden OR and DISTRIBUTION large increase in the number of flu patients? Will it be necessary to enforce “social distancing” to reduce the spread of epidemic flu? How will essential services be maintained? These are examples of issues for which the public health community will need to be© prepared. Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Other Significant Historical Developments Alexander Fleming, Alexander Langmuir, Wade Hampton Frost, and Joseph © Jones & BartlettGoldberger Learning, made several LLC other historically significant© contributions. Jones & Bartlett Scottish Learning, LLC NOT FOR SALEresearcher OR Fleming DISTRIBUTION is credited with discovering the antimicrobialNOT FOR properties SALE ofOR DISTRIBUTION the mold Pencillium notatum in 1928. This discovery led to development of the antibiotic penicillin, which became available toward the end of World War II. Langmuir, regarded as the father of infectious disease epidemiology, in 1949 established the epidemiology section of the federal agency presently © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC called the Centers for Disease Control and Prevention. This section later came NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION to be known as the Epidemic Intelligence Service (EIS), which celebrated its 50th anniversary in 2001 and is discussed later in this chapter. Frost, who held the first professorship of epidemiology in the United States beginning in 1930 at Johns Hopkins University, advocated the use of quantitative methods to illuminate© Jones public & Bartlett health problems, Learning, although LLC his concept of epidemiology© Jones & Bartlett Learning, LLC tendedNOT to FOR be restricted SALE narrowlyOR DISTRIBUTION to the study of infectious diseases. (Frost’sNOT FOR SALE OR DISTRIBUTION seminal work on cohort analysis is covered in Chapter 7.) Finally, Goldberger’s discovery of the cure for pellagra, a nutritional deficiency disease characterized by the so-called three Ds (dermatitis, diarrhea, and dementia), led to reduc- © Jones & Bartletttions in the Learning, occurrence ofLLC the disease, which had gained© Jonesattention & in Bartlett the early Learning, LLC NOT FOR SALE1900s. OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

R ECENT A PPLICATIONS OF E PIDEMIOLOGY 37

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTRecent FOR SALEApplications OR DISTRIBUTION of Epidemiology NOT FOR SALE OR DISTRIBUTION Epidemiologic activity has exploded during the past several decades.45 For example, the ongoing Framingham Heart Study, begun in 1948, is one of the pioneering research investigations of risk factors for coronary heart disease.46 © Jones & BartlettAnother Learning, development, LLC occurring after World War II,© was Jones research & on Bartlett the associ- Learning, LLC NOT FOR SALEation OR between DISTRIBUTION smoking and lung cancer.47 An exampleNOT is the FOR work SALE of Doll OR and DISTRIBUTION Peto,48 based on a fascinating study of British physicians. The computer and powerful statistical software have aided the proliferation of epidemiologic research studies. Popular interest in epidemiologic findings is also © Jones & Bartlett Learning,intense. LLC Almost every day now, one© encounters Jones & media Bartlett reports Learning, of epidemiologic LLC NOT FOR SALE OR DISTRIBUTIONresearch into such diverse health concernsNOT FOR as acquired SALE immune OR DISTRIBUTION deficiency syndrome, chemical spills, breast cancer screening, and the health effects of second- hand cigarette smoke. Table 1–2 reports triumphs in epidemiology; these are

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTTable 1–2FOR TriumphsSALE OR in Epidemiology DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Risk Factor Categories Disease Risk Factors Direction

Alcohol Esophageal cancer alcohol (interaction with smoking) IR Viruses Liver cancer hepatitis B virus IR © Jones & Bartlett Learning,Burkitt lymphoma LLC Epstein Barr virus© Jones & Bartlett IR Learning, LLC NOT FOR SALE OR DISTRIBUTIONKaposi sarcoma Herpes simplex virusNOT type FOR B SALE IROR DISTRIBUTION Cervical cancer something transmitted sexually IR (human papilloma virus) Nasopharyngeal carcinoma Epstein Barr virus IR Yellow fever “something transmitted IR by mosquitos” (Flavivirus) New variant (nv) prions (interaction with genotype) IR © Jones & Bartlett Learning, LLC Creutzfeldt-Jacob disease© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONBacteria Cholera NOT“something FOR inSALE water” (VibrioOR choleraDISTRIBUTION)IR Peptic ulcer Helicobactor pylori IR Puerperal fever “something on doctor’s hands” IR (group B Streptococcus) Nutrition Pellagra “something in bread” (niacin) P Neural tube defects folic acid, folate P Oral clefts folic acid P ©Occupation Jones & LungBartlett cancer Learning,asbestos LLC (interaction with smoking)© Jones IR & Bartlett Learning, LLC NOT FOR SALEBladder cancer OR DISTRIBUTIONaniline dye NOTIR FOR SALE OR DISTRIBUTION Mesothelioma asbestos IR Lung cancer asbestos (interaction with smoking) IR Angiosarcoma vinyl chloride IR Infertility (male) DBCP IR Nasal cancer nickel smelting IR Lung cancer “something in uranium mines” © Jones & Bartlett Learning, LLC (interaction with© Jonessmoking) & BartlettIR Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION continues

38 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

Risk Factor Categories Disease Risk Factors Direction

Environment Dental caries fluoride [deficiency] P © Jones & Bartlett Learning,Cancer LLC arsenic© Jones & Bartlett IR Learning, LLC Drugs/ NOT FOR SALEDevices OR DISTRIBUTION Myocardial infarction aspirinNOT FOR SALE P OR DISTRIBUTION Micoagthnia iso-retinene during pregnancy IR Pelvic inflammatory disease Dalkon Shield IUD IR Septic abortion Dalkon Shield IUD IR Hormones Clear cell adenocarcinoma diethylstilbestrol prenatally IR of the vagina © Jones & Bartlett Learning, LLC Venous thromboembolism© combined Jones estrogen/progestin & Bartlett Learning, IR LLC NOT FOR SALE OR DISTRIBUTION NOT(oral FOR contraceptives) SALE OR DISTRIBUTION Venous thromboembolism postmenopausal estrogen IR Ovarian cancer oral contraceptives P Endometrial cancer combined estrogen/progestin P Endometrial cancer oral contraceptives: IR postmenopausal estrogen Iron deficiency anemia oral contraceptives P © Jones Benign& Bartlett breast disease Learning, oral contraceptivesLLC © P Jones & Bartlett Learning, LLC NOT FORMyocardial SALE infarction OR DISTRIBUTION oral contraceptivesNOT IR FOR SALE OR DISTRIBUTION (interaction with smoking) Ischemic stroke oral contraceptives IR (interaction with hypertension; modified by dose) Genetics Breast cancer “something genetic” IR © Jones & Bartlett Learning, LLC (BRCA1, BRCA2 mutations)© Jones & Bartlett Learning, LLC Ovarian cancer “something genetic” IR NOT FOR SALE OR DISTRIBUTION (BRCA2 mutations)NOT FOR SALE OR DISTRIBUTION Colon cancer “something genetic” (APC1 mutations) IR Miscellaneous Toxic shock syndrome super absorbent tampons IR SIDS prone sleep position IR Reyes syndrome aspirin (interaction with infection) IR © Jones & Bartlett Learning,Smoking LLC Lung cancer ©smoking Jones & Bartlett Learning,IR LLC Coronary disease smoking IR NOT FOR SALE OR DISTRIBUTIONHemorrhagic strokeNOT smoking FOR SALE OR DISTRIBUTIONIR Ischemic stroke smoking IR Abdominal aortic aneurism smoking IR Peripheral vascular disease smoking IR Parkinson’s disease smoking P Ulcerative colitis smoking P © JonesLaryngeal & Bartlett cancer Learning,smoking LLC ©IR Jones & Bartlett Learning, LLC Intrauterine growth smoking during pregnancy IR NOT FOR retardationSALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Toxemia/pre-eclampsia smoking during pregnancy P

Abbreviations: IR, increased risk; P, protective (see Chapters 3, 6, and 7).

Source: Compiled by Diane Petitti. Adapted with permission from The Epidemiology Monitor, October © Jones & Bartlett2001, p. 6. Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

R ECENT A PPLICATIONS OF E PIDEMIOLOGY 39

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC examples in which epidemiologists have identified risk factors for cancer, heart NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION disease, infectious diseases, and many other conditions. One triumph in Table 1–2 is how epidemiology helped to uncover the association between the human papilloma virus and cervical cancer. On June 8, 2006, the FDA announced the licensing of the first vaccine (Gardisil®) to prevent cervical cancer caused by four © Jones & Bartletttypes of Learning,human papillomavirus LLC and approved its use© inJones females & aged Bartlett 9 to 26 Learning, LLC NOT FOR SALEyears. OR Returning DISTRIBUTION to Table 1–2, the reader should noteNOT that although FOR SALE many of OR the DISTRIBUTION terms used in the table have not yet been discussed in this book, later sections of the text will cover some of them. Additional examples of applications of epidemiology are provided below. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONInfectious Diseases in the CommunityNOT FOR SALE OR DISTRIBUTION Infectious disease epidemiology, one of the most familiar types of epidemiology, investigates the occurrence of epidemics of infectious and communicable diseases. Examples are studying diseases caused by bacteria, viruses, and microbio- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC logic agents; tracking down the cause of foodborne illness; and investigating new NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION diseases such as SARS and avian influenza (Exhibit 1–4). An illustration is the use of epidemiologic methods to attempt to eradicate, when possible, polio, measles, smallpox, and other communicable diseases. Another example is outbreaks of infectious diseases in hospitals (nosocomial infections). More infor- © Jones & Bartlettmation Learning,about this topic LLC is presented in Chapter 12.© The Jones role of & the Bartlett Epidemic Learning, LLC NOT FOR SALEIntelligence OR DISTRIBUTION Service in investigating disease outbreaksNOT is defined FOR as follows:SALE OR DISTRIBUTION The Epidemic Intelligence Service (EIS) is a corps of disease detectives who work for the Centers for Disease Control (CDC) in Atlanta, Georgia. The EIS consists of approximately 65 physicians, nurses, and other public health experts who are on © Jones & Bartlett Learning,call LLC 24 hours a day for two years. Up© to Jones 3,000 disease & Bartlett outbreaks occurLearning, each year inLLC NOT FOR SALE OR DISTRIBUTIONthe United States. EIS officers mayNOT be responsible FOR forSALE tracking OR down DISTRIBUTION unusual disease outbreaks in the United States as well as in foreign countries. For example, an outbreak of cholera in Guinea-Bissau, Africa, was linked to the body of a dock- worker smuggled home for burial. About half of the participants at a funeral feast for the deceased later developed cholera. Other investigative work has included: © Jonesmeasles outbreaks, & Bartlett hepatitis Learning, in a day care LLC center, tuberculosis in New York© City,Jones & Bartlett Learning, LLC NOTand FORLyme disease SALE in Connecticut. OR DISTRIBUTION The CDC monitors a wide range of healthNOT con- FOR SALE OR DISTRIBUTION ditions that include influenza epidemics, chronic diseases, such as heart disease, and AIDS.49

Health and the Environment © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEOccupational OR DISTRIBUTION exposure, air pollution, contaminatedNOT drinking FOR water, SALE accidental OR DISTRIBUTION injuries, and other environmental agents may affect human health. Occupational

40 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

Investigations into an outbreak of highly pathogenic avian influenza demonstrate the role of epidemiology in containing outbreaks of © Jones & Bartlettinfectious Learning, diseases LLC that threaten the health of© the Jones population. & Bartlett The Learning, LLC NOT FOR SALE ORarrival DISTRIBUTION of avian influenza (caused by the H5N1NOT virus) FOR that beganSALE in OR DISTRIBUTION EXHIBIT 1–4 the late 1990s is an example of the occurrence of an infectious disease with potential to impact a specific community as well as the entire world. This highly fatal condition worried public health authorities © Jones & Bartlett Learning,who wereLLC concerned that avian influenza© Jones could & createBartlett a worldwide Learning, pan- LLC NOT FOR SALE OR DISTRIBUTIONdemic, mirroring the 1918 pandemicNOT and FOR lesser SALEinfluenza OR epidemics DISTRIBUTION that occurred later in the 20th century. The emergence of a pandemic might be the consequence of mutation of the virus into a version that could be com- municated rapidly on a person-to-person basis. © BeginningJones & in Bartlett 1997, avian Learning, influenza appeared LLC in Hong Kong, with an© ini- Jones & Bartlett Learning, LLC tialNOT 18 humanFOR SALEcases, of OR which DISTRIBUTION 6 were fatal.50 These human cases coincidedNOT FOR SALE OR DISTRIBUTION with outbreaks among poultry on farms and in markets that sold live poultry. Authorities destroyed the entire chicken population in Hong Kong; subsequently, no additional human cases linked to the source in Hong © Jones & BartlettKong were Learning, reported. Two LLC additional human cases were© Jones reported & in Bartlett Hong Learning, LLC NOT FOR SALEKong OR in 2003 DISTRIBUTION and were associated with travel to mainlandNOT China.FOR SALE OR DISTRIBUTION The epidemic did not end in Hong Kong: additional cases began appearing in Southeast Asia during late 2003. Virus outbreaks involving animals and humans were limited primarily to Vietnam and some other areas of Southeast Asia (e.g., Thailand). One case of probable person-to- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC person spread of H5N1 virus is believed to have occurred in Thailand. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Then, in 2005, the virus manifested itself in central Asia, spreading to Europe, Africa, and the Middle East. From December 1, 2003, to April 30, 2006, nine countries reported a total of 205 laboratory-verified cases to the World Health Organization with 113 of these illnesses being fatal. At about© Jones the same & Bartlett time, infection Learning, with the virusLLC was reported among flocks© ofJones & Bartlett Learning, LLC domesticNOT FOR and SALEwild birds OR in 50DISTRIBUTION countries. NOT FOR SALE OR DISTRIBUTION Officials remain concerned that migrating flocks of wild birds that cover a vast geographical area could spread H5N1 to domestic poultry in many parts of the world (Figure 1–14).51 Humans who come into contact © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALEcontinues OR DISTRIBUTION

R ECENT A PPLICATIONS OF E PIDEMIOLOGY 41

FIGURE 1–14 Pathogenic avian influenza (H5N1) can appear in wild and domestic avian flocks. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEwith OR these DISTRIBUTION domestic birds would be at risk of contractingNOT FOR the highly SALE patho- OR DISTRIBUTION genic virus. The theoretical possibility remains that the virus could mutate into a form that is transmissible from person to person. Worldwide, epidemiologists have been involved with tracking and surveillance of the © Jones & Bartlett Learning,H5N1 LLC virus. By November 2007,© a Jonestotal of 335& Bartlett cases and Learning,206 deaths had LLC occurred worldwide. In 2007, Indonesia and Egypt accounted for more NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION than 80% of the 72 cases of avian influenza that were reported during that year.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION and environmental epidemiology address the occurrence and distribution of conditions such as dust diseases, occupational dermatoses, or diseases linked to harmful physical energy, such as ionizing radiation from x-ray machines or other © Jones & Bartlettsources. Learning, Many of the LLCdiseases studied by environmental© Jones epidemiologists & Bartlett have Learning, LLC NOT FOR SALEagent OR factors DISTRIBUTION and manifestations similar to those in NOToccupational FOR epidemiology,SALE OR DISTRIBUTION for example, the role of pesticides in causing environmentally associated illness.

42 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Injury control epidemiology studies risk factors associated with motor vehicle NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION accidents, bicycle injuries, falls, and occupational injuries. Study results may suggest preventive measures by modifying the environment. Reproductive and perinatal epidemiology investigates environmental and occupational exposures and birth outcomes. Related topics are sudden infant death syndrome, epidemi- © Jones & Bartlettology of neonatal Learning, brain hemorrhage, LLC early pregnancy, and© methodologicalJones & Bartlett issues Learning, LLC NOT FOR SALEin drug OR epidemiology. DISTRIBUTION Chapter 13 covers environmentalNOT and FOR occupational SALE OR DISTRIBUTION epidemiology.

© Jones & Bartlett Learning,Chronic LLC Disease, Lifestyle, and© HealthJones &Promotion Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONAn example of this category is the roleNOT of lifestyle FOR (e.g., SALE exercise, OR diet,DISTRIBUTION smoking, and alcohol consumption) in physical health outcomes such as obesity, coronary heart disease, arthritis, diabetes, and cancer. Hypothesized risk factors studied include antecedent variables within the person’s physical and psychosocial environment© Jones that may& Bartlett be associated Learning, with health LLC and disease. To illustrate, there© haveJones & Bartlett Learning, LLC beenNOT studies FOR of theSALE relationship OR DISTRIBUTION between obesity and the tendency of theNOT built FOR SALE OR DISTRIBUTION environment to dissuade people from walking. Also, poor dietary choices, smoking, substance abuse, and excessive alcohol consumption are linked to many chronic illnesses. Regarding the psychosocial environment, cultural practices © Jones & Bartlettaffect behaviors Learning, that are LLClinked to health and disease. More© Jones information & Bartlett about Learning, LLC NOT FOR SALEthis topic OR is presentedDISTRIBUTION in Chapters 4 and 15. NOT FOR SALE OR DISTRIBUTION

Psychological and Social Factors in Health © Jones & Bartlett Learning,Stress, socialLLC support, and socioeconomic© Jones status may& Bartlett affect mental Learning, health and LLC NOT FOR SALE OR DISTRIBUTIONphysical illnesses such as arthritis, someNOT gastrointestinal FOR SALE conditions, OR DISTRIBUTION and essential hypertension. A related area involves epidemiologic studies of personality factors and disease, exemplified by the type A personality and its potential link to heart disease. Psychiatric epidemiology is concerned with the distribution and determinants© Jones of mental & Bartlett illness. Examples Learning, are the LLCdefinition and measurement of© men- Jones & Bartlett Learning, LLC talNOT illness, FOR social factorsSALE related OR DISTRIBUTIONto mental illness, and urban and rural differencesNOT FOR SALE OR DISTRIBUTION in frequency of mental disorders. Major research studies have investigated the epidemiology of depressive symptomatology. Also studied are factors that affect the distribution of mental retardation, including certain genetic syndromes. © Jones & BartlettSocial, cultural, Learning, and demographic LLC factors (socioeconomic© status, Jones gender, & Bartlett employ- Learning, LLC NOT FOR SALEment, maritalOR DISTRIBUTION status, and race) are considered correlatesNOT of mental FOR health SALE status. OR DISTRIBUTION Chapter 15 considers this area in more detail.

S TUDY Q UESTIONS AND E XERCISES 43

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTMolecular FOR SALEand Genetic OR DISTRIBUTION Epidemiology NOT FOR SALE OR DISTRIBUTION Genetic epidemiology studies the distribution of genetically associated diseases among the population. For example, research on the genetic bases for disease hypothesized possible inherited susceptibility to severe alcoholism52 and to breast 53 © Jones & Bartlettand ovarian Learning, cancer. MolecularLLC epidemiology applies© the Jones techniques & Bartlett of molecu- Learning, LLC NOT FOR SALElar biology OR DISTRIBUTION to epidemiologic studies. An illustrationNOT is the FOR use of SALE genetic ORand DISTRIBUTION molecular markers, including deoxyribonucleic acid typing, to examine their influence upon behavioral outcomes and host susceptibility to disease. An overview of molecular and genetic epidemiology is provided in Chapter 14. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONConclusion NOT FOR SALE OR DISTRIBUTION

Epidemiology is the study of the distribution and determinants of diseases, states of health, disability, morbidity, and mortality in the population. Epidemiology, ©which Jones examines & Bartlett disease occurrence Learning, in the LLC population rather than in the© individ- Jones & Bartlett Learning, LLC NOTual, is sometimesFOR SALE called OR population DISTRIBUTION medicine. Several examples demonstratedNOT that FOR SALE OR DISTRIBUTION the etiologic bases of disease and health conditions in the population are often unknown. Epidemiology is used as a tool to suggest factors associated with occurrence of disease and to introduce methods to control disease in the population. © Jones & BartlettThree Learning, aspects characterize LLC the epidemiologic approach.© Jones The first & isBartlett quantifica- Learning, LLC tion, that is, counting of cases of disease and construction of tables that show NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION variation of disease by time, place, and person. The second is use of special vocabulary, for example, epidemic and epidemic frequency of disease. The third is its interdisciplinary composition, which draws from microbiology, biostatistics, social and behavioral sciences, and clinical medicine. © Jones & Bartlett Learning,The LLC historical antecedents of epidemiology© Jones & began Bartlett with Learning,Hippocrates, LLCwho NOT FOR SALE OR DISTRIBUTIONimplicated the environment as a factorNOT in diseaseFOR causation.SALE OR Second, DISTRIBUTION Graunt, one of the biostatistics pioneers, compiled vital statistics in the mid-1600s. Third, Snow used natural experiments to track a cholera outbreak in Golden Square, London. Finally, Koch’s postulates advanced the theory of specific disease agents. ©At Jonespresent, epidemiology& Bartlett isLearning, relevant to many LLC kinds of health problems© found Jones in & Bartlett Learning, LLC NOTthe community. FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Study Questions and Exercises © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR1. Using DISTRIBUTION your own words, give a definition ofNOT epidemiology. FOR SALE Before OR you DISTRIBUTION read Chapter 1, what were your impressions regarding the scope of

44 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC epidemiology? Based on the material presented in this chapter, what top- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ics are covered by epidemiology? That is, to what extent does epidemiology focus exclusively upon the study of infectious diseases or upon other types of diseases and conditions? 2. How would the clinical and epidemiologic descriptions of a disease differ, © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC and how would they be similar? NOT FOR SALE3. ToOR what DISTRIBUTION extent does epidemiology rely on medicalNOT disciplines FOR forSALE its con- OR DISTRIBUTION tent, and to what extent does it draw upon other disciplines? Explain the statement that epidemiology is interdisciplinary. 4. Describe the significance for epidemiology of the following historical © Jones & Bartlett Learning, developments:LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONa. associating the environmentNOT with diseaseFOR causalitySALE OR DISTRIBUTION b. use of vital statistics c. use of natural experiments d. identification of specific agents of disease ©5. Jones Explain & what Bartlett is meant Learning, by the following LLC components of the definition© Jones of & Bartlett Learning, LLC NOTepidemiology: FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION a. determinants b. distribution c. morbidity and mortality © Jones & Bartlett6. The Learning, following questions LLC pertain to the term epidemic.© Jones & Bartlett Learning, LLC NOT FOR SALE ORa. What DISTRIBUTION is meant by an epidemic? Give a definitionNOT in FORyour own SALE words. OR DISTRIBUTION b. Describe a scenario in which only one or two cases of disease may rep- resent an epidemic. c. What is the purpose of surveillance? © Jones & Bartlett Learning, d.LLC Give an example of a disease© that Jones has cyclic & Bartlett patterns. Learning, LLC NOT FOR SALE OR DISTRIBUTIONe. What is the epidemic thresholdNOT for FOR a disease? SALE In what OR sense DISTRIBUTION is it possible to conceive of the epidemic threshold as a statistical concept? 7. Epidemiologic research and findings often receive dramatic media cover- age. Find an article in a media source (e.g., The New York Times) on a © Jonestopic related & Bartlett to epidemiology. Learning, In a LLCone-page essay, summarize the© find- Jones & Bartlett Learning, LLC NOTings FOR and discussSALE how OR the DISTRIBUTION article illustrates the approach of epidemiologyNOT FOR SALE OR DISTRIBUTION to the study of diseases (health conditions) in populations. 8. During the next week, read your local or national newspaper carefully. Try to find the following terms used in newspaper articles; keep a record © Jones & Bartlettof themLearning, and describe LLC how they are used: © Jones & Bartlett Learning, LLC NOT FOR SALE ORa. epidemiology DISTRIBUTION NOT FOR SALE OR DISTRIBUTION b. epidemiologist

S TUDY Q UESTIONS AND E XERCISES 45

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC c. infectious disease NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION d. chronic disease e. clinical trial f. increased risk of mortality associated with a new medication 9. What is the definition of a natural experiment? Identify any recent exam- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC ples of natural experiments. To what extent might changes in legislation NOT FOR SALE ORto DISTRIBUTIONlimit smoking in public places or to increaseNOT the speedFOR limit SALE on high-OR DISTRIBUTION ways be considered natural experiments? 10. Review Exhibit 1–2, Snow on Cholera. What do you believe was the purpose of each of the following observations by Snow? © Jones & Bartlett Learning, LLCa. “small white, flocculent ©particles” Jones in &the Bartlett water from Learning, the Broad Street LLC NOT FOR SALE OR DISTRIBUTIONpump NOT FOR SALE OR DISTRIBUTION b. the location of cholera deaths as shown in Figure 1–8 c. people who died avoided the pump in Marlborough Street and instead had the water from the Broad Street pump © Jonesd. “the & Bartlettgreatest number Learning, of attacks LLC in any one day occurred on ©the Jones 1st of & Bartlett Learning, LLC NOT FORSeptember, SALE .OR . .” DISTRIBUTION NOT FOR SALE OR DISTRIBUTION e. “On September 8th—the day when the handle of the pump was removed . . .” To what extent do you think removing the pump handle was effective in stopping the disease outbreak? © Jones & Bartlett11. HowLearning, does quantification LLC support the accomplishment© Jones of the& Bartlettfour aims of Learning, LLC NOT FOR SALE ORepidemiology? DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 12. How did Koch’s postulates contribute to the advancement of epidemiology? To what extent is identification of specific agent factors a prerequi- site for tracking down the causes of disease outbreaks? © Jones & Bartlett Learning,13. LLC What are the characteristics© that Jones distinguish & Bartlett pandemic Learning, disease from LLCepi- NOT FOR SALE OR DISTRIBUTIONdemic disease? Name someNOT examples FOR ofSALE notorious OR DISTRIBUTIONpandemics that occurred in history. Why did the “Spanish Flu” of 1918 qualify as a pandemic? In giving your answer, be sure to distinguish among the terms epidemic, pandemic, and endemic. © Jones14. Identify & Bartlett some infectious Learning, diseases LLC that could reach pandemic occurrence© Jones & Bartlett Learning, LLC NOT FORduring SALE the 21st OR century. DISTRIBUTION What conditions do you believe exist atNOT present FOR SALE OR DISTRIBUTION that could incite the occurrence of pandemics? Why have public health officials been concerned about the emergence of new diseases such as “bird flu”? Speculate about what might happen to organized society and © Jones & Bartlett theLearning, health care LLC system should an outbreak of ©pandemic Jones influenza & Bartlett occur. Learning, LLC NOT FOR SALE15. OR The DISTRIBUTION Black Death that occurred during the MiddleNOT Ages FOR eradicated SALE a ORlarge DISTRIBUTION proportion of the world population at that time. Estimate how likely it

46 C HAPTER 1HISTORY AND S COPE OF E PIDEMIOLOGY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC would be for a similar epidemic of plague to develop during the current NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION decade. 16. In developed countries, many safeguards exist for the prevention of foodborne illness. Discuss how it would be possible for a foodborne illness outbreak such as the one caused by E. coli to erupt in a developed country. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION References

1. Centers for Disease Control and Prevention. Update on Multi-State Outbreak of E. coli O157:H7 Infections From Fresh Spinach, October 6, 2006. Available at: © Jones & Bartlett Learning, http://www.cdc.gov/foodborne/ecolispinach/100606.htm.LLC © Jones & Bartlett Accessed Learning, October 10, LLC NOT FOR SALE OR DISTRIBUTION2007. NOT FOR SALE OR DISTRIBUTION 2. Centers for Disease Control and Prevention. Ongoing multistate outbreak of Escherichia coli serotype O157:H7 infections associated with consumption of fresh spinach—United States, September 2006. MMWR. 2006;55:1045–1046. 3. State of California, Department of Health Services. CDHS E-Coli Update for Oct. 18, 2006. Available at: http://www.dhs.ca.gov/opa/ecoli. Accessed October 10, 2007. ©4. Jones U.S. Food & and Bartlett Drug Administration. Learning, FDA LLC News: FDA Statement on Foodborne©E. Jones coli & Bartlett Learning, LLC NOTO157:H7 FOR OutbreakSALE inOR Spinach DISTRIBUTION. Available at: http://www.fda.gov/bbs/topics/NEWS/NOT FOR SALE OR DISTRIBUTION 2006/NEW01489.html. Accessed October 10, 2007. 5. Centers for Disease Control and Prevention, Foodborne and Diarrheal Diseases Branch. Multistate outbreak of E. coli O157 infections, November–December 2006. Available at: http://www.cdc.gov/ecoli/2006/december/121406.htm. Accessed © Jones & BartlettOctober Learning, 10, 2007. LLC © Jones & Bartlett Learning, LLC NOT FOR SALE6. OR Karin DISTRIBUTIONM. Anthrax invades and evades the immune systemNOT to cause FOR widespread SALE infec- OR DISTRIBUTION tion. Environmental Health News, Highlights in Environmental Health Sciences Research, 2002 Highlights. Division of Extramural Research and Training, National Institute of Environmental Health Sciences. 2002:1–2. Available at: http://www .niehs.nih.gov/research/supported/sep/2002/anthrax.cfm. Accessed October 10, 2007. © Jones & Bartlett Learning,7. HughesLLC JM, Gerberding JL. Anthrax© bioterrorism: Jones & Lessons Bartlett learned Learning, and future direc- LLC NOT FOR SALE OR DISTRIBUTIONtions. Emerg Infect Dis [serial online].NOT 2002;8:1–4. FOR AvailableSALE at: OR http://www.cdc.gov/ DISTRIBUTION ncidod/EID/vol8no10/02-0466.htm. Accessed January 2, 2008. 8. Centers for Disease Control and Prevention. Update: Investigation of bioterrorism- related anthrax and interim guidelines for clinical evaluation of persons with possible anthrax. MMWR. 2001;50:941–948. ©9. Jones Maillard & J-M, Bartlett Fischer M, Learning, McKee KT Jr, LLC et al. First case of bioterrorism-related© Jones & Bartlett Learning, LLC inhalational anthrax, Florida, 2001: North Carolina investigation. Emerg Infect Dis NOT[serial FOR online]. SALE 2002;8(10). OR DISTRIBUTION Available at: http://www.cdc.gov/ncidod/EID/vol8no10/NOT FOR SALE OR DISTRIBUTION 02-0389.htm. Accessed October 10, 2007. 10. Centers for Disease Control and Prevention. Ongoing investigation of anthrax— Florida, October 2001. MMWR. 2001;50:877. 11. Centers for Disease Control and Prevention. Update: investigation of bioterrorism- © Jones & Bartlettrelated Learning, anthrax—Connecticut, LLC 2001. MMWR. 2001;50:1077–1079.© Jones & Bartlett Learning, LLC NOT FOR SALE12. OR Mathews DISTRIBUTION T, Lee ED. Outbreak of fear. Newsweek. 1995;NOT May 22:48, FOR 50. SALE OR DISTRIBUTION 13. Fear on Seventh Ave. Newsweek. 1978; September 18:30.

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