Epidemics-Pandemics-Outbreaks & Emerging Diseases Spring 2013

Ponder This! New diseases are being identified at an unprecedented rate (WHO) It would be extremely naive and complacent to assume that there will not be another disease like AIDS, Ebola, or SARS sooner or later. (WHO) The question of another pandemic of influenza is no longer a matter of IF; but of when. (WHO) Global control efforts have been seriously jeopardized by rise in drug resistant strains of diseases. (WHO)

COMMON SOURCE COMMON SOURCE PROPAGATED EPIDEMICS

Common Source Epidemics Point source Continuous source Common vehicle Vector borne epidemics

Common Source Epidemics Exposure to or from a single source? (point source/common vehicle) Common clues: – Rapid rise and fall on curve (front end loaded) – Outbreak from a single source (Person to person- index case) – Continued exposure to a single source

Common Source Epidemics

Propagated Outbreak Clues AKA as “progressive” outbreaks From multiple sources or exposures Multiple events or exposures) From inapparent sources (asymptomatic) Vector source (known or unknown) Animal reservoir or infection Back end loaded

Propagated Epidemic Outbreak of norovirus gastroenteritis at a university student residence – Edmonton, Alberta, 2006

Outbreak Investigation 10 Steps – This is a conceptual order – steps may be done at the same time – Step 1: Prepare for Field Work – Step 2: Establish the Existence of an Outbreak – Step 3: Verify the Diagnosis – Step 4: Define and Identify Cases – Step 5: Describe Data as Time, Place and Person – Step 6: Develop Hypotheses – Step 7: Evaluate Hypotheses – Step 8: Refine Hypotheses – Step 9: Implement Control/Prevention Measures – Step 10: Communicate Findings

Step 1: Prepare for Field Work Research, supplies & equipment – Research the disease and gather equipment for investigation Administrative arrangements – Make administrative/travel arrangements Local contacts – -contact all parties to determine roles

Step 2: Establish Existence of Outbreak Consider severity, potential for spread, public concern, and availability of resources Expected # cases per area – Health dept. records, hospital and death records Consider other factors – Numbers may exceed normal due to Better reporting Seasonal fluctuations Population changes

Step 3: Verify Diagnosis Proper diagnosis – Verify procedures used to diagnose – Check methods used for identifying agent Not lab error Commonality – Interview several persons who became ill to gain insight concerning cause, source, and spread

Step 4: Define and Identify Cases Case Definition Clinical information Characteristics of affected Location Time sequence Identification of specific cases Confirmed: lab verification Probable: many factors for diagnosis but no lab verification Possible: some factors point to diagnosis

Step 5: Describe Data in Time, Place and Person Time – Epidemic curve (histogram of outbreak) Place – geographic extent plus spot map of cases Person – identify the affect population by host factors

Step 6: Develop Hypotheses Agent – Capable of causing disease & its source Host – Person susceptive to agent Environment – Allows them to come together NEED A TESTABLE HYPOTHESIS

Step 7: Evaluate Hypotheses Analytical Study – Cohort or Case Control – Two by two table calculations

Step 8: Refine Hypotheses If no confirmation of initial hypotheses, need to look for new vehicle or mode of transmission May need to be more specific Verify with laboratory studies to validate hypothesis

Step 9: Implement Control/ Prevention Measures ASAP! – Must know agent, source, susceptible host, transmission Aim to break chain of transmission at any point – May interrupt transmission or exposure – May reduce suceptibility

Step 10: Communicate Findings Oral briefing – Inform local health officials or other need-to know groups ASAP Written report – Usually done in scientific format for future reference

Global Outbreak Alert and Response Network WHO overseen collaboration (UN organizations, Red Cross, international NGOs) Operational framework to stay alert to the threat of outbreaks Objectives – Combat international spread of outbreaks – Ensure technical assistance reaches affected areas rapidly – Contribute to long-term preparedness

WHO Pandemic Phases Global preparedness plan. Defines stages of pandemic Outlines WHOs role Recommendations for national measures 6 stages – Stages 1-3 – preparedness – Stages 4-6 – need for response

WHO Pandemic Phases

How Serious is the Pandemic? Depends on: Number infected Severity of disease (virulence) Vulnerability of population Effectiveness of preventive measures

Pandemic Severity Index Developed by CDC -- For United States 5 categories (1 best; 5 worst) Based on initial estimate of number of expected deaths (CFR – case fatality rate) Conditions: - Case fatality rate - Projected number of deaths

Pandemic Severity Index

Emerging Infectious Diseases

WNV

Monkeypox from Prairie Dogs

Are infectious diseases emerging more than before?

Defined emerging infections as: “New, reemerging or drug-resistant infections whose incidence in humans has increased within the past two decades or whose incidence threatens to increase in the near future.” Institute of Medicine 1992 Report on Emerging Infections

Human demographics and behavior Human demographics and behavior Technology and Industry Technology and Industry Economic development and land use Economic development and land use International travel and commerce International travel and commerce Microbial adaptation and change Microbial adaptation and change Breakdown of public health measures Breakdown of public health measures Major Factors Contributing to Emerging Infections: 1992 Institute of Medicine Report, 1992

 Human vulnerability  Climate and weather  Changing ecosystems  Poverty and social inequality  War and famine  Lack of political will  Intent to harm More Factors Contributing to Emerging Infections: 2003 Institute of Medicine Report, 2003

 More populations with weakened immune system: elderly, HIV/AIDS, cancer patients and survivors, persons taking antibiotics and other drugs Emerging Infections: Human Demographics, Behavior, Vulnerability More people, more crowding Changing sexual mores (HIV, STDs) Injection drug use (HIV, Hepatitis C) Changing eating habits (foodborne infections)

 Mass food production (Campylobacter, E.coli O157:H7, etc…)  Use of antibiotics in food animals (antibiotic-resistant bacteria) Emerging Infections: Technology and Industry New drugs for humans (prolonging vulnerability)

 Changing ecology influencing waterborne, vectorborne transmission (e.g. dams, deforestation) Emerging Infections: Economic Development, Land Use, Changing Ecosystems Contamination of watershed areas by cattle (Cryptosporidium) More exposure to wild animals and vectors (Lyme disease)

 Persons infected with an exotic disease anywhere in the world can be into major US city within hours (SARS, VHF,…)  Foods from other countries imported routinely into US (Cyclospora,….)  Vectors hitchhiking on imported products (Asian tiger mosquitoes on lucky bamboos,….) Emerging Infections: International Travel and Commerce

Speed of Global Travel in Relation to World Population Growth From: Murphy and Nathanson. Semin. Virol. 5, 87, 1994 CDC

 Increased antibiotic resistance with increased use of antibiotics in humans and food animals (VRE, VRSA, penicillin- and macrolide-resistant Strep pneumonia, multidrug-resistant Salmonella, TB,….)  Jumping species from animals to humans (avian influenza, HIV, SARS?) Emerging Infections: Microbial Adaptation and Change

 Lack of basic hygienic infrastructure (safe water, foods)  Inadequate vaccinations (measles, diphtheria) Emerging Infections: Poverty, Social Inequality, Breakdown of Public Health Measures Discontinued mosquito control efforts (dengue, malaria) Lack of monitoring and reporting (SARS

 Bioterrorism: Anthrax in US 2001  Bio-Crimes: Salmonella in OR, Shigella in TX.  Potential agents: Smallpox, Botulism toxin, Plague, Tularemia, …. Emerging Infections: Intent to Harm

{ CDC

{ Prevention of Emerging Infectious Diseases Will Require Action in Each of These Areas  Surveillance and Response  Applied Research  Infrastructure and Training  Prevention and Control CDC

{ Preventing Emerging Infectious Diseases: More to Do  Enhance communication: locally, regionally, nationally, globally  Increase global collaboration  Share technical expertise and resources  Provide training and infrastructure support globally  Ensure political support  Ensure judicious use of antibiotics  Vaccines for all

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{ Preventing Emerging Infectious Diseases Surveillance and Response Detect, investigate, and monitor emerging pathogens, the diseases they cause, and the factors influencing their emergence, and respond to problems as they are identified. CDC

{ Preventing Emerging Infectious Diseases Applied Research Integrate laboratory science and epidemiology to increase the effectiveness of public health practice. CDC

{ Preventing Emerging Infectious Diseases Infrastructure and Training Strengthen public health infrastructures to support surveillance, response, and research and to implement prevention and control programs. Provide the public health work force with the knowledge and tools it needs. CDC

{ Preventing Emerging Infectious Diseases Prevention and Control Ensure prompt implementation of prevention strategies and enhance communication of public health information about emerging diseases. CDC