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)

COMMONSOURCE

COMMONSOURCE

PROPAGATEDPROPAGATED

EPIDEMICSEPIDEMICS

Common SourceEpidemics

• 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 WNV

Monkeypox from Prairie Dogs Monkeypox from Prairie Dogs

Are infectious diseases Are infectious diseases emerging more than emerging more than before? before?

Defined emerging infections as: Defined emerging infections as: “New, reemerging or drug-resistant “New, reemerging or drug-resistant infections whose incidence in infections whose incidence in humans has increased within the humans has increased within the past two decades or whose past two decades or whose incidence threatens to increase in incidence threatens to increase in the near future.”the near future.”

Institute of Medicine 1992 Report on Institute of Medicine 1992 Report on Emerging InfectionsEmerging Infections

• Human demographics and behaviorHuman demographics and behavior• Technology and IndustryTechnology and Industry• Economic development and land useEconomic development and land use• International travel and commerceInternational travel and commerce• Microbial adaptation and changeMicrobial adaptation and change• Breakdown of public health measuresBreakdown of public health measures

Major Factors Contributing Major Factors Contributing to Emerging Infections: 1992to Emerging Infections: 1992

Institute of Medicine Report, 1992

Human vulnerabilityHuman vulnerability Climate and weatherClimate and weather Changing ecosystemsChanging ecosystems Poverty and social inequalityPoverty and social inequality War and famineWar and famine Lack of political willLack of political will Intent to harmIntent to harm

More Factors Contributing to More Factors Contributing to Emerging Infections: 2003Emerging Infections: 2003

Institute of Medicine Report, 2003

More populations More populations with weakened with weakened immune system: immune system: elderly, HIV/AIDS, elderly, HIV/AIDS, cancer patients and cancer patients and survivors, persons survivors, persons taking antibiotics and taking antibiotics and other drugs other drugs

Emerging Infections:Emerging Infections:Human Demographics, Behavior, VulnerabilityHuman 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 Mass food production (Campylobacter, E.coli (Campylobacter, E.coli

O157:H7, etc…)O157:H7, etc…) Use of antibiotics in food Use of antibiotics in food

animals (antibiotic-resistant animals (antibiotic-resistant bacteria)bacteria)

Emerging Infections:Emerging Infections:Technology and IndustryTechnology and Industry

•New drugs for humans (prolonging vulnerability)

Changing ecology Changing ecology influencing influencing waterborne, waterborne, vectorborne vectorborne transmission (e.g. transmission (e.g. dams, deforestation) dams, deforestation)

Emerging Infections:Emerging Infections:Economic Development, Land Use, Changing Economic Development, Land Use, Changing EcosystemsEcosystems

•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 Persons infected with an exotic disease anywhere in the world can be into major US city within hours (SARS, VHF,…)world can be into major US city within hours (SARS, VHF,…)

Foods from other countries imported routinely into US Foods from other countries imported routinely into US (Cyclospora,….)(Cyclospora,….)

Vectors hitchhiking on imported products (Asian tiger Vectors hitchhiking on imported products (Asian tiger mosquitoes on lucky bamboos,….)mosquitoes on lucky bamboos,….)

Emerging Infections:Emerging Infections:International Travel and CommerceInternational Travel and Commerce

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Speed of Global Travel in Relation toWorld Population Growth

From: Murphy and Nathanson. Semin. Virol. 5, 87, 1994CDC

Increased antibiotic resistance with increased use of Increased antibiotic resistance with increased use of antibiotics in humans and food animals (VRE, VRSA, antibiotics in humans and food animals (VRE, VRSA, penicillin- and macrolide-resistant Strep pneumonia, penicillin- and macrolide-resistant Strep pneumonia, multidrug-resistant Salmonella, TB,….)multidrug-resistant Salmonella, TB,….)

Jumping species from animals to humans (avian influenza, Jumping species from animals to humans (avian influenza, HIV, SARS?)HIV, SARS?)

Emerging Infections:Emerging Infections:Microbial Adaptation and ChangeMicrobial Adaptation and Change

Lack of basic hygienic infrastructure (safe water, foods)Lack of basic hygienic infrastructure (safe water, foods) Inadequate vaccinations (measles, diphtheria)Inadequate vaccinations (measles, diphtheria)

Emerging Infections:Emerging Infections:Poverty, Social Inequality, Breakdown of Public Poverty, Social Inequality, Breakdown of Public Health MeasuresHealth Measures

• Discontinued mosquito control efforts (dengue, malaria)• Lack of monitoring and reporting (SARS

Bioterrorism: Anthrax in US 2001Bioterrorism: Anthrax in US 2001 Bio-Crimes: Salmonella in OR, Shigella in TX.Bio-Crimes: Salmonella in OR, Shigella in TX. Potential agents: Smallpox, Botulism toxin, Plague, Potential agents: Smallpox, Botulism toxin, Plague,

Tularemia, ….Tularemia, ….

Emerging Infections:Emerging Infections:Intent to HarmIntent to Harm

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CDC

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Prevention of Emerging Infectious Prevention of Emerging Infectious Diseases Will Require Action in Diseases Will Require Action in Each of These AreasEach of These Areas

Surveillance and ResponseSurveillance and Response

Applied ResearchApplied Research

Infrastructure and TrainingInfrastructure and Training

Prevention and ControlPrevention and Control

CDC

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Preventing EmergingPreventing EmergingInfectious Diseases: More to DoInfectious Diseases: More to Do

Enhance communication: locally, regionally, nationally, globallyEnhance communication: locally, regionally, nationally, globally

Increase global collaborationIncrease global collaboration

Share technical expertise and resourcesShare technical expertise and resources

Provide training and infrastructure support globallyProvide training and infrastructure support globally

Ensure political supportEnsure political support

Ensure judicious use of antibioticsEnsure judicious use of antibiotics

Vaccines for allVaccines for all

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Preventing EmergingPreventing EmergingInfectious DiseasesInfectious Diseases

Surveillance and ResponseSurveillance and ResponseDetect, investigate, and monitor emerging Detect, investigate, and monitor emerging

pathogens, the diseases they cause, and the pathogens, the diseases they cause, and the

factors influencing their emergence, and factors influencing their emergence, and

respond to problems as they are identified.respond to problems as they are identified.

CDC

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Preventing EmergingPreventing EmergingInfectious DiseasesInfectious Diseases

Applied ResearchApplied ResearchIntegrate laboratory science and Integrate laboratory science and

epidemiology to increase the epidemiology to increase the

effectiveness of public health effectiveness of public health

practice.practice.

CDC

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Preventing EmergingPreventing EmergingInfectious DiseasesInfectious Diseases

Infrastructure and TrainingInfrastructure and Training

Strengthen public health infrastructures Strengthen public health infrastructures to support surveillance, response, and to support surveillance, response, and research and to implement prevention research and to implement prevention and control programs. and control programs.

Provide the public health work force with Provide the public health work force with the knowledge and tools it needs.the knowledge and tools it needs.

CDC

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Preventing EmergingPreventing EmergingInfectious DiseasesInfectious Diseases

Prevention and ControlPrevention and ControlEnsure prompt implementation of Ensure prompt implementation of

prevention strategies and enhance prevention strategies and enhance

communication of public health communication of public health

information about emerging diseases.information about emerging diseases.

CDC