Foundations of Global Health Learning Objectives • Identify components of the disease triangle Communicable Diseases (Part 1): and links in the chain of transmission • Define prevention, control, elimination, Control & Smallpox Eradication eradication and extinction for infectious diseases • Identify eradication indicators • Outline successful interventions against

[When] we were beginning the global program, there was a communicable diseases (smallpox) feeling amongst scientists that you could not eradicate an organism. There was a view that organisms-- there’s an • ecology they fit into, in a kind of way that’s been around for Define the International Health Regulations years and years-- and to eliminate them is impossible…. Nature, that lovely lady to whom eradicating malaria was failing. So to take on a second we owe polio, leprosy, smallpox, • Identify Nationally Notifiable Diseases eradication program and have that fail as well would reflect syphilis, tuberculosis, cancer... very badly on the World Health Organization. ~Dr. Stanley Cohen ~Dr. DA Henderson, Director 1966-1977, WHO Smallpox Eradication Campaign 2

Importance of Communicable Diseases Communicable Disease Definitions • Over 13 million people die each year from infectious and parasitic diseases • Immensely important to the global burden of disease – Most important burden of disease in Sub-Saharan Africa • Poor people, women, children, and the elderly are the most vulnerable • Enormous economic An estimated 13.6 million died in 2008 consequences from an infectious • Much of burden disease unnecessary • Relevance to MDGs

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Disease Triangle Chain of Infection

• Need host, pathogen & environment to produce disease • Multiple external factors can influence this cycle – Reservoir – Vectors – Abiotic conditions – Culture & behavior • Model to visualize transmission of a communicable disease from its source (reservoir) to a susceptible host

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1 Pathogen Reservoir

Pathogen Pathogen Reservoir

• Disease causing agent • Habitat where infectious agent normally lives – Human: symptomatic or asymptomatic – Animal: zoonotic – Non-living (environmental): plants, soil, and water contribute to life cycle

Malaria Smallpox Polio HIV (top) & Tuberculosis 7 8

Portal of Exit Transmission

• How pathogens are passed Pathogen Pathogen Reservoir Reservoir Portal Portal of of Exit Exit Transmission

• Path by which an agent • Direct • Indirect leaves the reservoir • Direct contact • Airborne or source host • Droplet spread • Vehicleborne • Vectorborne

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Portal of Entry New Host

• Agent enters susceptible host Pathogen Pathogen Reservoir Reservoir Portal Portal of of Exit Exit • Portals: Transmission Portal Transmission Portal – Respiratory of of New Entry Entry – Oral Host – Skin • Final link is a susceptible host – Intravenous – Gastrointestinal

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2 Basic Reproductive Ratio (R0) Herd Immunity

• R0 definition: expected number of secondary infections arising from a single individual Sustained during his or her entire infectious period, in a transmission population of susceptibles Transmitting Susceptible Transmitting Susceptible case case

Transmission terminated Transmitting Immune Susceptible Case (A) (B) (C) (Indirectly Protected)

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Herd Immunity Thresholds for Selected Vaccine-Preventable Diseases Help– It’s Contagious! Immunization Levels • How do we stop these Disease Ro Herd 1999 1997-1998 ERADICATION Immunity 19-35 Pre-School diseases that can Months Diphtheria 6-7 85%* 83%* 9% “reproduce”? ELIMINATION Measles 12-18 83-94% 92% 96% Mumps 4-7 75-86% 92% 97% CONTROL Pertussis 12-17 92-94% 83%* 97% Polio 5-7 80-86% 90% 97% PREVENTION Rubella 6-7 83-85% 92% 97% Smallpox 5-7 80-85% __ __

*4 doses † Modified from Epid Rev 1993;15: 265-302, Am J Prev Med 2001; 20 (4S): 88-153, MMWR 2000; 49 (SS-9); 27-38 16

Disease Prevention Disease Control

• Reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts • Need continued intervention measures to maintain control

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3 Elimination Eradication & Extinction • Reduction to zero of the incidence (new cases) of disease or infection in a defined • Eradication: permanent reduction to zero of geographical area worldwide incidence of disease or infection • Need continued surveillance and measures to – Intervention measures no longer needed prevent re-establishment of transmission – Smallpox • Extinction: infectious agent no longer exists in nature or in laboratory – NONE

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Control Elimination st Reducing infection, cases, deaths and Reducing the number of cases and new The 1 Smallpox Vaccination illness due to a disease. "Acceptable" infections to zero. Efforts often focus on Jenner 1796 levels of disease may vary by region. a defined geographical area in which the infectious agent is endemic. Consistent, sustained prevention and Cowpox lesions on the hand of Sarah Nelmes treatment interventions are necessary Continued intervention measures are to ensure ongoing reduction of illness. required to ensure that the infectious (case XVI in Jenner’s Inquiry), from which agent does not re-emerge in a region material was taken for the vaccination of James that has experienced elimination. Phipps below in 1796

Examples: diarrheal diseases, Examples: tetanus, poliomyelitis, onchocerciasis (Africa), malaria, leprosy, lymphatic filariasis, measles, tuberculosis onchocerciasis in Americas

Eradication Extinction Permanent worldwide elimination of an The specific infectious agent no longer infectious agent in nature - no new exists in nature or in the laboratory. infections or cases of disease. The agent may exist in designated Examples: None laboratories.

After a period of years, intervention measures are no longer needed.

Examples: Smallpox Source: CDC. 21

Smallpox Endemic Areas 1945 Smallpox Endemic Areas 1967

Endemic smallpox Endemic Importations Transmission Interrupted

4 R & D Contributions Smallpox Eradication Strategy

1. Mass vaccination campaigns in each country, using vaccine of ensured potency that would reach >80% of population. 2. Development of a system to detect Bifurcated Needle 98%+ take and contain cases and outbreaks. Freeze-Dried Smallpox Vaccine † Henderson DA, Moss B, Smallpox and Vaccinia in Vaccines, 3rd edition, 1999

Mass Vaccination Surveillance and Containment Strategy

• Search for cases Contacts to Contacts • Containment of spread by vaccinating primary Contacts to Case(s) contacts and their Case(s) contacts • Most efficient strategy

Progression of Smallpox Progression of Smallpox

Source: Foege, Lane, and Millar, Am J. Epi, 1969 Source: Foege, Lane, and Millar, Am J. Epi, 1969

5 Last Cases of Smallpox**

Rahima Banu – 16 October 1975 Ali Maow Maalin – 26 October 1977 Variola Major-Bangladesh Variola Minor-Somalia ** Two laboratory acquired cases occurred in UK in 1978

Why Worry About Smallpox?

• Allegations that Soviet BW program produced smallpox virus for use in bombs and ICBMs 1980 • Concerns that smallpox virus could be obtained and used by others as terrorist weapon JAMA 1999; 281: 2127-2137

The Faces of Smallpox Eradication: Principle Indicators

• Effective intervention is available to interrupt transmission of the agent • Practical diagnostic tools are available to detect levels of infection that can lead to transmission • Humans are essential for life-cycle of agent – no other vertebrate reservoir – does not amplify in the environment

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6 ITFDE 7 Candidates • Targeted six infectious diseases for eradication – mumps, polio, rubella, guinea worm disease, lymphatic filariasis, and cysticercosis – And, now measles! • Eradication is defined as “reduction of the

worldwide incidence of Adapted from CDC, Morbidity and Mortality Weekly Report 42 (1993): 1-25 a disease to zero”

©2010 Jones & Bartlett Publishers, LLC 37 38

Measles

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Not Now Not Possible

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7 Obstacles to Elimination Control At the International Level The World Health Organization (WHO) • Non-human reservoirs • Headquarters in Geneva, Switzerland; 193 member • Asymptomatic cases nations • Uses sophisticated systems of surveillance and • Drug resistance communication to keep track of microbial diseases on a • Weak health systems global level – Influenza surveillance network; • Vaccine safety concerns identifies strains to include – Autism fears in annual vaccine – Impotency • Assists countries in control of diseases – Contamination • Sets priorities and standards for disease treatment and allocation of resources 44 43 ©2010 Jones & Bartlett Publishers, LLC

WHO’s innovative International Health Regulations approach to • Only binding international agreements on disease global disease control surveillance • Framework to prevent international spread of disease through effective national surveillance and coordination of response to public health emergencies – Maximum protection, minimum restriction • IHR 1969 only applied to traditionally "quarantinable" diseases – Cholera, plague, and yellow fever • Restricted surveillance to info provided by governments

Adapted from Grein, T.W., et al., Emerging Infectious Diseases 6 (2000): 97-102. 45 ©2010 Jones & Bartlett Publishers, LLC 46

IHR 2005 • More effective against global disease threats • Require countries to report certain disease outbreaks and public health events to WHO • Enforced in 2007

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8 National Notifiable Infectious Diseases (2007) Practice Questions

AIDS/HIV Haemophilus influenzae Rabies Anthrax Hansen disease (leprosy) Rocky Mountain spotted fever • Define case, case fatality rate. Arbovirus disease Hantavirus pulmonary Rubella *California serogroup virus syndrome Salmonellosis • What are the components of the disease triangle? *Eastern equine encephalitis virus Hemolytic uremic syndrome SARS-CoV disease *Powassan virus Hepatitis A, acute Shiga toxin-producing Escherichia coli (STEC) • What are links in the chain of transmission? *St. Louis encephalitis virus Hepatitis B Shigellosis *West Nile virus Hepatitis C Smallpox • What is the basic reproductive rate? *Western equine encephalitis virus Influenza mortality Streptococcal disease Botulism Legionellosis Syphilis • Define prevention, control, elimination, eradication, Brucellosis Listeriosis Tetanus extinction. Chancroid Lyme disease Toxic-shock syndrome (non-streptococcal) Chlamydia trachomatis Malaria Trichinellosis • What strategies were used to eradicate smallpox? What Cholera Measles Tuberculosis Coccidioidomycosis Meningococcal disease Tularemia indicators made it possible? Cryptosporidiosis Mumps Typhoid fever Cyclosporiasis Novel influenza A virus infxn Staphylococcus aureus • Define the international health regulations. What diseases Diphtheria Pertussis *Vancomycin-intermediate (VISA) were reportable under IHR 1969? IHR 2005? Ehrlichiosis Plague *Vancomycin-resistant (VRSA) Giardiasis Poliovirus Varicella infection • Name 5 nationally notifiable diseases in the United States. Gonorrhea Psittacosis Yellow fever Q fever

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In Summary…

• Infectious diseases represent a major burden on public health • Prevention, control and elimination are possible in significantly reducing this burden for many diseases • Eradication of infectious diseases are more challenging • Proven success story for eradication of smallpox… can it be repeated? • International Health Regulations and reporting of notifiable diseases will aid these efforts

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