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Population Health
for
Health Professionals
EMERGING INFECTIOUS
DISEASES
PART 1
Purpose

The purpose of this module is to provide
an exposure to some of the emerging
diseases that will affect the health of the
public and to examine the challenges
and opportunities they pose to the
public health system
At the completion of this
module you will be able to
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Describe the causes and contributing factors
which lead to the emergence of infectious
diseases.
Describe the latest emerging infections
which have the potential to threaten people
living in the United States.
Describe some of the measures that can be
used to control and contain these diseases
What Are Emerging
Infectious Diseases?
These are human illnesses caused
by microorganisms or their
poisonous byproducts and having
the potential for occurring in
epidemic numbers.
Why are we concerned about
Emerging Infectious Diseases?
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These diseases:
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Pose a threat to all persons
regardless of age, sex, lifestyle,
ethnic background, or socioeconomic
status
Cause suffering and death
Impose a financial burden on society
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Over the past century, infectious diseases have
decreased as a cause of death in this country
Improved sanitation, vaccination and antibiotics
have played a large part in this decrease and
are responsible to the increase in the lifespan
of our residents
However, in the past twenty years the incidence
of emerging infectious diseases has increased
FACTORS RELATED TO THE EMERGENCE OF
INFECTIOUS DISEASES
Factors studied
Examples
1. Biological----------Genes, microbes, medicines, vaccines, blood and organ
transplants, rapid microbial adaptation and resistance to antibiotics
2. Behavior----------Sports, nutrition, sexuality, tobacco, alcohol, international travel
3. Environment: physical--------Air, water, toxins, radiation, pollution, noise,
agricultural development, climate change, technology
4. Environment: social ---------Housing, education, employment,
conditions
and working
5. Environment: human rights-------Discrimination, war, torture,
physical and mental abuse, lack of access to health care, prevention and
health education
6. Breakdown of traditional basic public health infrastructure
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An existing organism given the selective
advantage by such things as a changing
environmental condition and given the
opportunity can infect a new host
population
An organism can re-emerge in a drug
resistant form
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In the US, about 25% of physician visits
are attributed to infectious diseases
In 1993, direct and indirect costs were
estimated to be more than $120 billion.
Today, these costs are substantially
more
Economic and Societal Impact of
Some Infectious Diseases
Economic and Social Impact of
Some Infectious Diseases
How Are Infectious
Diseases Acquired?
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Inhalation
Ingestion
 Food, water, soil
Percutaneous inoculation
Absorption from mucous membranes
Exposure to blood and body fluids
CDC’s Target Areas
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Antimicrobial resistance
Foodborne and waterborne diseases
Vectorborne and zoonotic diseases
Diseases transmitted through blood
transfusions or blood products
Chronic diseases caused by infectious
agents
CDC’s Target Areas (cont.)
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Vaccine development and use
Diseases of persons with impaired host
defenses
Diseases of pregnant women and
newborns
Diseases of travelers, immigrants, and
refugees
CONTROL MEASURES
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Water treatment
Vector control
Rodent reduction
Vaccination
Antibiotics
ROLE OF PUBLIC HEALTH
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Surveillance and early response (detect,
investigate, initiate action and monitor)
Assessment of health status, risks, and
services available to a community
Development of health policy
Assurance of quality services (discourage
inappropriate use of antibiotics)
Laboratory identification
ROLE OF PUBLIC HEALTH
(CONT.)
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Rapid communication with medical providers
and hospitals
Communication with the media
Public and health care provider education
(role in transmission, modification of lifestyle
to avoid disease, etc.)
Environmental assessment and remediation,
e.g. food inspection, water supply inspection,
vector control)
EMERGING INFECTIOUS
DISEASES
PART 2
New Emerging
Infectious Diseases
The following diseases have recently emerged
as public health concerns and will be discussed
more fully in the slides that follow:
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Atypical Influenza
Severe Acute Respiratory Syndrome (SARS)
West Nile encephalitis (WNV)
Monkey Pox
Ebola
Hantavirus
INFLUENZA and ATYPICAL
INFLUENZA
Influenza: USA annual stats
• 10-20 % of population contract influenza annually
• 36,000 die (excess mortality), more than 90% are 65
and older
• 226,000 hospitalizations (2004 data)
• 38 million missed school days, 70 million missed
work days
• $ 1-3 Billion in direct costs
R. Ball, MD, MPH
Worldwide 3 to 5 million people
are infected with influenza each
year with 250,000 to 500,000
deaths
Major Influenza Pandemics
of the Twentieth Century
Major Years
Subtype
Excess US
Mortality
’17-’18
H1N1
550,000
’57-’58
H2N2
70,000
’68-69
H3N2
36,000
NEXT
? H5N1 (Avian)
?
Influenza Surface Proteins
Neuraminidase (N)
Hemagglutinin (H)
RNA
(highly mutagenic)
M2 protein
(only on type A)
The Usual Human Influenza A
Strains within the Last Century
Major influenza
surface antigens: H1
Hemagglutinin
Neuraminidase
H2
H3
N1
H1N1
H2N1
H3N1
N2
H1N2
H2N2
H3N2
Asian Flu Hong Kong Flu
1920
1957
H1N1
H2N2
H3N2
Thanks to Eric Brenner, MD for slide.
1968
1977
2003
The Wider Family of Influenza
Critters
15H x 9N 135 potential HN combinations
*H5N1 already spreading in SE Asia (mortality 1 in 2);
inefficient person-person transmission; USA is developing a
limited vaccination program vs. A/ H5N1 “Avian Flu”
H1
H2
H3
H4
H5
H6
H7
H8
H9
H10
H11
H12
H13
H14
H15
N1
H1N1
H2 N1
H3N1
N2
H1N2
H2N2
H3N2
N4
N5
N6
N7
*H5N1
*
Slide by Eric Brenner, MD & R. Ball, MD, MPH
N8
N9
Emergence of New Influenza A Virus Subtypes in Humans
Thanks to JJ Gibson, MD for graph.
Some Confirmed Instances of Avian
Influenza Infecting Humans since 1997 (*)
Year
1997
1999
2002
2003
2003
2003
2003
2004
2004
Virus
H5N1
H9N2
H7N2
H5N1
H7N7
H9N2
H7N2
H5N1
H7N3
Location
Hong Kong
Hong Kong
Virginia
Hong Kong
Netherlands
Hong Kong
New York
Thailand, Vietnam
Canada
Summary tally:
H5N1: 3
H7N2: 2
H7N3: 1
H7N7: 1
H9N2: 2
Is this virus actively
reassorting its genes
to achieve a unique
combination of
virulence and
communicability?
(*) For details see: www.cdc.gov/flu/avian/gen-info/avian-flu-humans.htm
Thanks to Eric Brenner, MD for slide.
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Avian influenza A (H5N1) that infects poultry
is a concern due to the potential for spread of
an influenza A variant to humans, and the
eventuality of human to human transmission,
and a pandemic of atypical influenza.
Recent reports from several Asian countries
that are experiencing Asian “flu” outbreaks in
flocks of chickens indicate that humans have
been infected who live or work in close
proximity to those flocks of chickens
Avian Influenza may well be
the pandemic in waiting
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Even if an epidemic is not deliberately
caused by an altered strain of influenza
virus, an epidemic or pandemic
originating from natural origins will more
than likely occur
If Pandemic Influenza Came Today...
 Up to 200 million people infected
 Up to 50 million people requiring care
 Up to 2 million hospitalizations
 Between 100,000 and 500,000 deaths
…just in the USA
“THE INFLUENZA CLOCK IS TICKING, WE
JUST DON’T KNOW WHAT TIME IT IS”
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Ed Marcuse, MD and past chairman, The
National Vaccine Advisory Committee
SARS (SEVERE ACUTE
RESPIRATORY SYNDROME)
A Novel Virus: SARS
NEJM May 15,
2003
SARS-BASIC FACTS
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SARS is an illness which can vary in severity
and is caused by a Corona virus most likely of
animal origin, e. g. civet
The disease is spread by large respiratory
droplets from sneezing and coughing within a
radius of 6 to 8 feet.
Incubation period-3 to 10 days
It can survive on surfaces up to 3 days but is
easily killed by standard disinfectants
SARS: Summary Points - 1
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In retrospect epidemic started ~ November 2002
in Southern China
WHO issues “Global Alert” March 2002
February 2003 very infectious patient infects many
guests at Metropole Hotel in Hong Kong who in
turn spread SARS to their own countries
World attention remained focused on SARS until
global surveillance shows all chains of
transmission interrupted ~ July 2003
MMWR March 28, 2003 / Vol. 52 / No. 12
Hong Kong Metropole Hotel index case. Example of a “super-spreader”.
Is there a small subset of SARS patients who
account for a disproportionate share of
transmission? MMWR May 9, 2003 / Vol. 52 / No. 18 - I
Patients No: 1, 6, 35,
130&127 seemed to be
“hypertransmitters”
SARS news: www.cnn.com
Thursday
May 15,
2003
R. Ball, MD, MPH
WHO consensus document on the
epidemiology of SARS :
Selected conclusions
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The report found no evidence that SARS is an
airborne disease
Health Care Workers were at special risk,
especially those involved with aerosol-generating
procedures
The risk of transmission is greatest around day 10
of the illness
Children were rarely affected by SARS
The implications of the events at the Metropole
Hotel are not yet fully understood
The Return of SARS--2004
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SARS reoccurred in China in 2004
There were nine cases
WHO issued a Global Health Advisory
The outbreak was contained 5/18/04,
but WHO advised continued vigilance
The return of SARS - 2004
Summary Comments
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SARS improved the ability of public health to
conduct surveillance, investigate, and establish
control measures for an infectious respiratory
disease with (then) apparently pandemic
potential
How extraordinary to have lived through the first
global outbreak which was managed in realtime by means of public health measures, the
Internet, and teleconferencing calls (e.g.
The return of SARS - 2004
Summary Comments
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How extraordinary to have lived through the first
global outbreak which was managed in realtime by means of public health measures, the
Internet, and teleconferencing calls (e.g.
between WHO, CDC, Hong-Kong, Singapore,
Toronto, etc.)
SARS “over its peak” ?
June 5 & 19,
2003
R. Ball, MD, MPH
SARS: we’re “unprepared”
www.gao.gov
http://www.gao.gov/new.items/d031058t.pdf
R. Ball, MD, MPH
WEST NILE VIRUS
FACTS ABOUT WNV
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West Nile Fever is a “flu-like” illness of sudden
onset, caused by a subgroup of viruses called
Flavoviruses
Symptoms: fever, sore throat, headache,
malaise, arthralgia or myalgia. Rash is
common.
Complications: meningitis or encephalitis
(inflammation of the brain tissue or the
covering of the brain) can occur. The disease
is then named West Nile neuroinvasive disease
Reservoir: certain birds
FACTS ABOUT WNV
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Incubation period: usually 3 to 12 days
Communicability: no direct person to
person transmission Mode of transmission:
the bite of an infected mosquito
Prevention: Mosquito eradication, mosquito
repellents
Treatment: none specific
Mortality rate: 3 to 15%
West Nile Virus:
a novelty becoming endemic
West Nile Virus:US 2003-CDC
MONKEY POX
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Monkey pox, an Orthopox virus caused
infection, closely resembles small pox clinically
Recently transmitted to humans by prairie
dogs infected by a Gambian giant rat imported
from Africa
Symptoms: fever, rash, muscle aches, cough
Mortality: 1 to 10% in Africa, none in the US
MONKEY POX
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Transmission: person to person has
occurred
Treatment: antibiotics, small pox
vaccination if early in the course of the
disease
Prevention: small pox vaccination is
partially successful, public education about
the dangers of illegally imported pets
A New
Infectious
Disease
Outbreak
NEJM 350:4, 1-22-04
The next two diseases, Ebola
and Hantaviral pulmonary
disease, are caused by a
group of similar viruses. They
are generally classified as
Hantaviral diseases.
EBOLA
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Mode of transmission: handling infected
wild animals
Incubation period: 2 to 21 days
Transmission: may be spread person to
person by contact with body secretions
Treatment: supportive
Prevention: caution in contact with
infected monkeys
SUDAN
2004: 20
cases and 5
deaths
Outbreak
coming under
control now…
HANTAVIRUS PULMONARY
SYNDROME
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Hantavirus pulmonary syndrome or hanta virus
disease is caused by a Sin Nombre virus which has
its reservoir in certain varieties of mice, principally
the deer mouse.
Infected rodents shed virus in urine, droppings and
saliva. Humans become ill when breathing in dried
aerosolized mouse excreta.
Symptoms: range from mild to severe. Fever,
myalgias, gastrointestinal complaints, pneumonia
Complications: blood dyscrasias, respiratory failure
and shock
EBOLA
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This is a severe viral illness caused by the
Ebola virus (Filoviridae family) with its reservoir
in chimpanzees and gorillas
Symptoms: sudden onset of fever, myalgia,
headache, followed by vomiting, diarrhea, and
rash.
Mortality: from 50 to 90 % in Africa
Complications: In severe forms, multiorgan
failure occurs, primarily hemorrhagic and
pulmonary complications
HANTAVIRUS PULMONARY
SYNDROME (CONT.)
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Mortality: up to 50%
Incubation period: a few days to six
weeks
Communicability: no human to human
transmission
Treatment: supportive
Prevention: rodent control, public
education and caution
There are other infectious agents that will
be the emerging infectious diseases of the
future. We must be vigilante as a society
and do our best to prevent their emergence
by learning the lessons that the diseases
we are dealing with today are teaching us.
YOUR ROLE IN DETECTION
OF EMERGING INFECTIONS
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Participate in surveillance activities in
your clinical setting
Know your resources and who to call for
consultation
Report to local health department
Note to the reader
Having just completed the module
“Emerging Infectious Diseases”, you
should proceed with either modules (5b)
“Environmental Impacts on Health” or (5c)
“The Future of Health and Health Care”
or
Proceed with the modules on Bioterrorism
At the completion of modules
5(b & c) you will be able to:
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Describe how various components of the environment
affect the public’s health
Identify the roles and responsibilities of the health care
provider in confronting health care threats related to the
environment
Discuss the health care needs of individuals and
communities in the future
Identify roles and responsibilities of different
components of the public health system in confronting
health challenges
At the completion of modules titled “Bioterrorism South Carolina at Risk” and “Bioterrorism - South
Carolina Responds”, you should be able to:
•Understand the concept of terrorism
•Understand how biological agents can be used as terrorist
weapons
•Describe the characteristics of those biologic agents
thought to be the choice of terrorists
• Understand the regional response to a bioterrorist act and
the use of the unified incident/management command
system
• Describe the role and responsibility of each responding
agency
• Raise other issues that must be dealt with in planning a
response to a bioterrorist act