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Introduction to Infectious Disease Epidemiology Kenrad Nelson, MD Johns Hopkins University Section A History of Infectious Diseases in the 20th Century Crude Death Rate* for Infectious Diseases: U.S., 1906–’96 40 states have health departments *Per 100,000 population per year §American Water Works Association. (1973). Water chlorination principles and practices: AWWA manual M20. Denver, Colorado. Adapted by CTLT from Armstrong, G. L., Conn, L. A., Pinner, R. W. (1999). Trends in infectious disease mortality in the United States during the 20th century. Journal of the American Medical Association, 281, 61–66. 4 Crude Death Rate* for Infectious Diseases: U.S., 1906–’96 First continuous municipal use of chlorine in water in U.S.§ *Per 100,000 population per year §American Water Works Association. (1973). Water chlorination principles and practices: AWWA manual M20. Denver, Colorado. Adapted by CTLT from Armstrong, G. L., Conn, L. A., Pinner, R. W. (1999). Trends in infectious disease mortality in the United States during the 20th century. Journal of the American Medical Association, 281, 61–66. 5 Crude Death Rate* for Infectious Diseases: U.S., 1906–’96 Influenza pandemic *Per 100,000 population per year §American Water Works Association. (1973). Water chlorination principles and practices: AWWA manual M20. Denver, Colorado. Adapted by CTLT from Armstrong, G. L., Conn, L. A., Pinner, R. W. (1999). Trends in infectious disease mortality in the United States during the 20th century. Journal of the American Medical Association, 281, 61–66. 6 Crude Death Rate* for Infectious Diseases: U.S., 1906–’96 First use of penicillin Salk vaccine introduced *Per 100,000 population per year §American Water Works Association. (1973). Water chlorination principles and practices: AWWA manual M20. Denver, Colorado. Adapted by CTLT from Armstrong, G. L., Conn, L. A., Pinner, R. W. (1999). Trends in infectious disease mortality in the United States during the 20th century. Journal of the American Medical Association, 281, 61–66. 7 Crude Death Rate* for Infectious Diseases: U.S., 1906–’96 *Per 100,000 population per year §American Water Works Association. (1973). Water chlorination principles and practices: AWWA manual M20. Denver, Colorado. Adapted by CTLT from Armstrong, G. L., Conn, L. A., Pinner, R. W. (1999). Trends in infectious disease mortality in the United States during the 20th century. Journal of the American Medical Association, 281, 61–66. 8 10 Leading Causes of U.S. Deaths: 1900 and 1997 The 10 leading causes of death as a percentage of all deaths in the United States, 1900 and 1997 1990 1997 1. Pneumonia 1. Heart Disease 2. Tuberculosis 2. Cancer 3. Diarrhea & Enteritis 3. Stroke 4. Heart Disease 4. Chronic Lung Disease 5. Stroke 5. Unintentional Injury 6. Liver Disease 6. Pneumonia & Influenza 7. Injuries 7. Diabetes 8. Cancer 8. HIV Infection 9. Senility 9. Suicide 10. Diptheria 10. Chronic Liver Disease Source: Morbidity and Mortality Weekly Report, 48(29), 623. 9 U.S. Death Rates for Common Infectious Diseases Death Rates for Common Infectious Diseases in the United States in 1900, 1935, and 1970 Mortality rate per 100,000 population 1900 1935 1970 Influenza and pneumonia 202.2 103.9 30.9 Tuberculosis 194.4 55.1 2.6 Gastroenteritis 142.7 14.1 1.3 Diphtheria 40.3 3.1 0.0 Typhoid fever 31.3 2.7 0.0 Measles 13.3 3.1 0.0 Dysentery 12.0 1.9 0.0 Whooping cough 12.0 3.7 0.0 Scarlet fever (including 9.6 2.1 0.0 streptococcal sore throat) Meningococcal infections 6.8 2.1 0.3 10 Mean Annual Death Rate from Whooping Cough Children under 15 years of age, England and Wales It is frequently assumed that the identification of the causative organisms and the development of vaccines and antibiotics are the reasons that mortality has changed, but this is not quite true for most infectious diseases. 11 Surgeon General’s Prediction “Because infectious diseases have been largely controlled in the United States, we can now close the book on infectious diseases.” — William Stewart, MD U.S. Surgeon General, 1967 12 Some Recent Epidemics of Emerging Infectious Diseases 13 Trends in Deaths Caused by Infectious Diseases United States,1980–1992 National Center for Health Statistics underlying and multiple cause-of-death data 14 Trends in Deaths Caused by Infectious Diseases, by Age United States,1980–1992, by age group National Center for Health Statistics underlying and multiple cause-of-death data 15 Death Trends Caused by Infectious Disease Syndromes United States,1980–1992 National Center for Health Statistics underlying and multiple cause-of-death data 16 Section B Newly Emerging Infections Trends in Death Rates from Leading Causes, Ages 25–44 Trends in annual rates of death from leading causes of death among persons 25–44 years old, United States, 1982–1998 18 Some Emerging AIDS-Related Infectious Diseases 1. Pneumocystis carinii 6. Cryptosporidium pneumonia 7. Microsporidium 2. Tuberculosis 8. Cryptococcus neoformans 3. Mycobacterium-avium 9. Penicillium marneffei complex 10. Disseminated salmonella 4. Kaposi’s sarcoma (HHV-8) 11. Bacillary angiomatosis 5. HSV-2 (Bartonella henselae) 12. HPV 19 Some Emerging Non-AIDS-Related Infectious Diseases 1. SARS 9. E. Coli O157:H7 2. West Nile disease 10. Antibiotic-resistant 3. Variant CJD disease – Pneumococci 4. Monkey pox – Staph-aureus 5. Ebola and Marburg viruses – Gonococci 6. Dengue – Salmonella 7. Influenza H5/N1 (?) 11. Cryptosporidium 8. Hanta virus 12. Anthrax 20 Chain of SARS Transmission at Hong Kong Hotel, 2003 The 8500 cases and 850 deaths worldwide were related to 1 case. A physician from southern China who checked into a hotel in Hong Kong was ill with pneumonia and infected 13 other people, probably through airborne transmission. The 13 infected persons were on their way to other countries and introduced the epidemic to others upon arrival at their destinations. − Canada − United States Ireland − − Thailand Singapore − − Vietnam 21 SARS Epidemic Curve in Hong Kong, 2003 22 Epidemic Curve for Beijing SARS Outbreak 23 Factors Leading to Emergence of Infectious Diseases AIDS Industrial commercial Population growth agriculture Speed and ease of travel War and social disruption Dam building Relocation of animals Global climate change Growth of daycare Increased antibiotic use for Aging of the population humans and animals Human-animal contact Encroachment of human populations on forest habitats 24 Emerging Infectious Diseases Related to Animal Contact Emerging Infectious Diseases Related to Direct Contact between Humans and Animals Disease Animal 1. HIV-1, LHIV-2 Primates (Africa) 2. Influenza Water fowl, pigs, chickens (N5/N1) 3. Ebola Primates (“bush meat”) 4. Marburg Primate (“bush meat”) 5. Hanta virus Deer mouse 6. Arena virus Various rodents 7. Variant CJD Cattle 8. Cryptosporidia Cattle 9. Hendra virus Fruit bats 10. Nipah virus Pigs, fruit bats 11. SARS Civet cats 12. Monkey pox Prairie dogs 25 Emergence of New Infectious Diseases Over the last 150 years, there have been many global changes that have enhanced the probability of the emergence of new infectious diseases of humans and animals. This chart depicts three examples of such trends: the increase in the human population, the increased construction of large dams (over 75 meters high) built in the U.S. (1890–1975), and the decrease in time needed to circle the globe. 26 Cryptosporidium Infection in Milwaukee, 1993 Reported date of the onset of illness in cases of laboratory-confirmed or clinically defined cryptosporidium infection— March 1 through April 15, 1993 Note: The clinically defined cases were identified during a telephone survey begun on April 9 of residents in the area served by Milwaukee Water Works 27 Turbidity of Treated Water in Milwaukee, 1993 Maximal turbidity of treated water in southern water-treatment plants of the Milwaukee Water Works, March 2 through April 28, 1993 28 Public Health Burden of Foodborne Disease Each year an estimated 76 million cases − One in four Americans gets a foodborne illness each year − One in 1,000 Americans is hospitalized each year − $6.5 billion in medical and other costs 3.5 million cases, 33,000 hospitalizations, and 1,600 deaths are caused by the pathogens: − Salmonella − E. Coli O157 and other STEC − Campylobacter − Listeria − Toxoplasma 29 Effect of Irradiation on Foods Free radical oxidants damage DNA of microbes Nothing becomes radioactive At doses up to 7.5 kiloGray, minimal change on taste, texture, nutritional value Shelf life in general is prolonged (because spoilage organisms are reduced) Effective in meats, poultry, grains, produce Exceptions include: − Sprout seeds may not sprout well if irradiated − Oysters die if irradiated, which shortens shelf life − Egg whites go milky and liquid − Grapefruit gets mushy 30 Foods Approved for Irradiation in the U.S. Year Food Dose (kGy) Purpose 1963 Wheat flour 0.2–0.5 Mold control 1964 White potatoes 0.05–0.15 Inhibit sprouting 1986 Pork 0.3–1.0 Trichinosis Shelf life and insect 1986 Fruit and vegetables 1.0 control 1986 Herbs and spices 30 Sterilization Bacterial pathogen 1990 (FDA) Poultry 3.0 reduction Bacterial pathogen 1992 (USDA) Poultry 1.5–4.5 reduction Bacterial pathogen 1997 (FDA) Fresh meat 4.5 reduction Bacterial pathogen 2000 (USDA) Fresh meat 4.5 reduction 31 Number of Outbreak-Related Cases of Escherichia coli Number of outbreak-related cases of Escherichia coli O157:H7 Reported to the CDC 32 E.