EMERGING INFECTIOUS DISEASES:
Introduction
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Age-Specific Mortality and Proportion of All Deaths Due to 9
Infectious Diseases
Source: JAMA 1999;281:61-66
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“During the postwar era American enjoyed unchallenged hegemony and unprecedented affluence….the economy hummed so smoothly that the nation had enough left over to fund a massive war on poverty…..” –Bruce J. Schulman, The Seventies —
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Background
Optimism about infectious diseases
Vaccinations decreased rates of many diseases
Measles
Mumps
Polio
Others
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Optimism
Antibiotics
Strep and rheumatic fever
Bacterial pneumonia
Many others
Elimination of one feared disease: smallpox
Combination of:
Vaccination
Prudent strategies
International cooperation
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Optimism Led to…..
Surgeon General Declares in 1967 that
Infectious diseases have been conquered
Attention needs to be devoted mostly to chronic diseases and diseases of lifestyle
Beginning of erosion of public health system—designed for infectious diseases
Decrease in funding in infectious disease training and research
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Consequences
Public health surveillance ill-prepared for any new threats
Only most senior clinicians and public health officials had adequate training in infectious disease
Government structure ill-prepared
Public thought that serious infections thing of past
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Lurking in the Background….
Infections have always been part of human experience
Evolved system of co-existence between microbes and humans
Growing international ties could introduce new pathogens through…….
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Triangle of Human Ecology (of Disease)
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The Early 1990’s
HIV/AIDS had been thought of as isolated problem but…
Hantavirus in Four Corners;
Cryptosporidiosis in Milwaukee;
E. coli 0157:H7 in Washington and Oregon
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“A Fragile Equilibrium”
“A careful review of infectious disease trends shows a fragile equilibrium between humans and infectious microorganisms.”
–David Satcher, Surgeon General, EID, 1995
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MAJOR NEW
JOURNAL 1995
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“EMERGING INFECTIOUS DISEASES: WHAT ARE THEY?
New infections resulting from changes or evolution of existing organisms
Known infections spreading to new geographic areas or populations
Previously unrecognized infections appearing in areas undergoing ecologic transformation
Old infections reemerging as a result of antimicrobial resistance in known agents or breakdowns in public health measures.
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1ST MAJOR REPORT
ON EMERGING
INFECTIONS
INSTITUTE OF
MEDICINE
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“It is this committee’s considered opinion that that the next major infectious agent to emerge as a threat to health in the United States, may, like HIV, be a pathogen that has not been previously recognized—” Institute of Medicine, 1992
In Fact…
HIV/AIDS not an isolated problem;
Public health community began waking up to
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Causes of Emergence
Changing demographics
Changing travel patterns—commerce
Host (human) behavior
Technological change
Ecological and climate change
Microbial change
Breakdown in a buffer—public health
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INSTITUTE
OF MEDICINE
REPORT
2003
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Source: Emerging Inf Dis, April 2016 (cdc.gov/eid)
Drivers of Threat, EID April 2016
Factors of Emergence in IOM-2
Microbial adaptation and change
Human susceptibility to infection
Climate and weather
Changing ecosystems
Economic development and land use
Intent to harm
Technology and industry
International travel and commerce
Breakdown of public health
War and famine
Lack of political will
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“SARS: A Very
21st Century Disease”
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Selected Emerging Infectious Diseases
Souce: NIAID of NIH
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Temporal Distn EIDs
Source: Jones et al, Nature, Feb 2008
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Relative Risk of EID Event
Source: Jones et al., Nature, Feb 2008.
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Changing Behavior
Demography and population geography—
Where people are
Behavior:
What people do, how they live and act
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Injectable Drug Use (IDU)
Nobody really knows why it happens
Related to:
Poverty
Affluence
Peer pressure
Psychological factors
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Property of IDU
It is addictive physically;
It is habituating psychologically;
It gets to be a major “need”
It is a commodity;
People will seek to minimize cost—
NEEDLE SHARING
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Diseases Associated With IDU
Hepatitis C–bloodborne
up to 3 million Americans
Over 10,000 deaths/yr
Only solution: liver transplants
Hepatitis B—bloodborne, sexual, vertical
Other forms of hepatitis
HIV/AIDS
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HIV/AIDS and Drug Use
Up to 35% of those entering drug treatment programs are HIV positive;
What about those who do not seek treatment?
25% of new cases of HIV/AIDS in US due to IDU
50% of women w/HIV due to IDU
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Technology and Industry
Food processing
E. coli 0157:H7
Listeriosis
Botulism
BSE (mad cow disease) and vCJD
Others
Air transportation
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Technology and Industry
Food processing
E. coli 0157:H7
Listeriosis
Botulism
BSE (mad cow disease) and vCJD
Others
Air transportation
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HIV/AIDS
Emergence from African rainforest;
Species transfer;
Diffusion through truck drivers;
Intercontinental diffusion
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Travel and Pathogens
Americans traveling abroad
Foreigners coming to US through:
Immigration
Travel
Cargo could serve as “vector” of pathogens
Airplanes
Ships
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Movement of Goods
Containerization and movement of goods;
Increasing role of foreign trade in the economy;
Specific data are in the book
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Container ship
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Examples of Disease Spread Due to Commodity Shipment
Aedes albopictus to Houston;
Ebola among monkeys, Virginia
“Airport malaria”
Imports of food
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“Perhaps the greatest problem associated with international commerce and its relation to disease emergence is the lack of appropriate, widely available diagnostic tests to allow effective screening of animals and products made in animals) that are destined for investigational use”—Institute of Medicine
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Thus there….
Is a tremendous need for social scientific involvement
Disease ecology is a blend of social science, ecology, and microbiology
If the problem is fundamentally social, it must be treated in social terms
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Long History of Travel and Disease
Introduction of the “Black Plague” into Europe from Asia;
The “Columbian” Exchange—
Introduction of smallpox to the Americas;
Possible introduction of syphilis in Europe;
Numerous influenza pandemics
Smallpox
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The roles of travel and commerce are not new, but the speed at which it is a major force is much greater
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Types of Travel
International
Has received most attention—interest in globalization and “permeable” borders;
Domestic—
Has received less attention in context of emerging diseases
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International Travel
>500 million international travelers/year;
>110 million intercontinental travelers;
>500,000 international flights/year
Actual data are difficult to derive
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Institute of Medicine Predictions
Lassa Fever may be introduced to US, other countries;
Malaria and other vector-borne diseases may be reintroduced
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Changing Demographics
Tremendous population growth
Urbanization;
Suburban growth (peripheral growth)
Growth at edge of city
Intersection with ecological change—
Contact of population with new biogeographical areas
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Urbanization
Concentration of more people into denser settlements;
Cities as “microbe magnets” –Laurie Garrett The Coming Plague
Factors promoting emergence in cities—
Density
Behavior
Poverty
Recent migration
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Planning
No integration of urban planning with health care needs;
No cooperation between sectors such as:
Urban sprawl;
Economic development;
Mosquito abatement;
Sewers and water….and
HEALTH CARE!
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Challenges
Understand what underlies emerging diseases;
Develop public health structure—
Training
Surveillance and detection
Disease control
Flexibility of understanding and response
Difference between public health and clinical medicine
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Optimism Led to…..
Surgeon General Declares in 1960’s that
Infectious diseases have been conquered
Attention needs to be devoted mostly to chronic diseases and diseases of lifestyle
Beginning of erosion of public health system—designed for infectious diseases
Decrease in funding in infectious disease training and research
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Consequences
Public health surveillance ill-prepared for any new threats
Only most senior clinicians and public health officials had adequate training in infectious disease
Government structure ill-prepared
Public thought that serious infections thing of past
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Lurking in the Background….
Infections have always been part of human experience
Evolved system of co-existence between microbes and humans
Growing international ties could introduce new pathogens through…….
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General Factors in Transmission
Ecological setting
Behavior
Host characteristics
Population characteristics
Movement
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Factors of Emergence in IOM-2
Microbial adaptation and change
Human susceptibility to infection
Climate and weather
Changing ecosystems
Economic development and land use
Intent to harm
Technology and industry
International travel and commerce
Breakdown of public health
War and famine
Lack of political will
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Factors of Emergence in IOM-2
Microbial adaptation and change
Human susceptibility to infection
Climate and weather
Changing ecosystems
Economic development and land use
Intent to harm
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Technology and industry
International travel and commerce
Breakdown of public health
War and famine
Lack of political will
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Emerging Diseases
New diseases;
Newly discovered diseases;
Re-emerging diseases;
Diseases that are spreading to new regions;
Diseases that are increasing in intensity