Download Infectious_epidemiology

General concepts:
1. Epidemiological triangle: the traditional model of infectious disease causation,
which has three components: an external agent, a susceptible host, and an environment
that brings the host and agent together so that disease occurs.
An external agent (organism):
- Ability of the agent to survive outside the host/ in the environment
- Ability of the agent to change its antigenicity to escape host’s immunity such as
influenza virus
A susceptible host:
- Personal factors such as low immunity, extremely age and malnutrition status
- Person with genetic predisposing factors
- Risk behaviors such as smoking, alcohol drinking, unsafe sex and some recreational
activities
An environment:
- Some favorable physical/ biological factors for vectors such as ambient temperature,
specified climate and disaster
- Limited social welfare/ poverty
- Displacement, immigrant
2. Isolation VS. Quarantine:
Isolation: separation, for the period of communicability, of infected persons (sick person)
or animals from others under such conditions as to prevent or limit the transmission of
the infectious agent from those infected to those who are susceptible or who may spread
the agent to others.
Quarantine: restriction of the activities of well persons or animals who have been
exposed to a case of communicable disease during its period of communicability (i.e.,
contacts) to prevent disease transmission during the incubation period if infection should
occur.
Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford
University Press. Kindle Edition.
3. Direct VS. Indirect transmission:
Direct transmission: direct and essentially immediate transfer of infectious agents to a
receptive portal of entry through which human or animal infection may take place. This
may be by direct contact such as touching, kissing, biting, or sexual intercourse or by the
direct projection (droplet spread) of droplet spray.
Indirect transmission:
Vehicle-borne: Contaminated inanimate material or objects (fomites--e.x., sharing
needles) such as toys, handkerchiefs, soiled clothes, bedding, cooking or eating utensils,
and surgical instruments or dressings (indirect contact); water, food, milk; biological
products including blood, serum, plasma, tissues, or organs; or any substance serving as
an intermediate means by which an infectious agent is transported and introduced into a
susceptible host through a suitable portal of entry. The agent may or may not have
multiplied or developed in or on the vehicle before being transmitted.
Vector-borne:
(a) Mechanical: Includes simple mechanical carriage by a crawling or flying
insect through soiling of its feet or proboscis or by passage of organisms through its
gastrointestinal tract. This does not require multiplication or development of the
organism.
(b) Biological: Propagation (multiplication), cyclic development, or a
combination of these (cyclopropagative) is required before the arthropod can transmit
the infective form of the agent to humans.
Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford
University Press. Kindle Edition.
Hep B= direct and indirect, Hep C= indirect (needle exchange)
Rabies= direct transmission from animal to human
Malaria= indirect (mosquito), a transmission cycle in between human and mosquito
Lepto= indirect reservoir. host is animals
4. Horizontal VS. Vertical transmission:
Horizontal transmission: the transmission of an infectious agent, such as bacterial, fungal,
or viral infection, between members of the same species that are not in a parent-child
relationship.
Reference: http://en.wikipedia.org/wiki/Horizontal_disease_transmission
Vertical transmission: (Syn: intergenerational transmission) the transmission of infection
from one generation to the next, especially of HIV infection from mother to infant
prenatally, during delivery, or in the postnatal period via breast milk.
Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford
University Press. Kindle Edition.
Vertical -Perinatal - Placental - Transplacental such as “TORCHS” - Toxoplasmosis,
Rubella, Cytomegalovirus, Herpes, Syphilis
5. Infectivity VS. Pathogenicity VS. Virulence
Infectivity: the proportion of people who are exposed to an agent and become infected.
Pathogenicity: the proportion of people who are infected by an agent and then develop
clinical disease.
Virulence: the measure of severity of a disease, expressed as the proportion of people
with the disease who become extremely ill or die.
* Are exposed – Become infected—Developed clinical disease—Become extremely
ill/die*
* Measle has high infectivity.
TB has low pathogenicity.
Rabies has high pathogenicity.
HIV has low infectivity, but high pathogenicity.
6. Zoonosis/ Enzootic or Epizootic: a disease infection, or infestation transmitted under
natural conditions from vertebrate animals to humans. Examples include rabies and
plague.
Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford
University Press. Kindle Edition.
7. Epidemic VS. Endemic VS. Pandemic:
Epidemic: [from the Greek epi (upon), dēmos (people)] The occurrence in a community
or region of cases of an illness, specific health-related behavior, or other health-related
events clearly in excess of normal expectancy. The community or region and the period
in which the cases occur must be specified precisely. The number of cases indicating the
presence of an epidemic varies according to the agent, size, and type of population
exposed; previous experience or lack of exposure to the disease; and time and place of
occurrence.
Endemic: the constant occurrence of a disease, disorder, or noxious infectious agent in a
geographic area or population group; it may also refer to the chronic high prevalence of a
disease in such area or group.
Pandemic: an EPIDEMIC occurring over a very wide area, crossing international
boundaries, and usually affecting a large number of people. Only some pandemics cause
severe disease in some individuals or at a population level. Characteristics of an
infectious agent influencing the causation of a pandemic include: the agent must be able
to infect humans, to cause disease in humans, and to spread easily from human to
human.
Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford
University Press. Kindle Edition.
8. Passive VS. Active immunity:
Passive immunity: conferred by an antibody produced in another host and acquired
naturally by an infant from its mother or artificially by administration of an antibodycontaining preparation (antiserum or immune globulin).
Reference: A Dictionary of Epidemiology (Kindle Locations 8206-8212). Oxford
University Press. Kindle Edition.
Active immunity: A type of immunity or resistance developed in an organism by its own
production of antibodies in response to an exposure to an antigen, a pathogen or to a
vaccine.
Reference: http://www.biology-online.org/dictionary/Active_immunity
Disease
Legionnaires’ disease
Causative agent
Bacterium
Reservoir
Man-made water supplies that aerosolized water
Mode of
Transmission
Air-borne spread
Incubation period
2-10 days (most often 5-6 days)
Risk factors
Aging, Compromised immunity, Chronic Lung Disease (COPD),
Deficiency of Immunity, Male
Preventive
measure
Proper maintenance and disinfection of man-made water supplies
Vaccination
No
Disease
Syphilis
Gonorrhea
Chlamydia
Causative
agent
Bacterium
Reservoir
Humans
Mode of
Transmission
Sexual
transmission
Vertical/ perinatal
transmission
Blood transfusion
Sexual
transmission
Vertical/
perinatal
transmission
Sexual transmission
Vertical/ perinatal
transmission
Incubation
period
10 days - 3 months 1-14 days
(Usually 3 weeks)
7-14 days
Risk factors
All people
Health
professionals
MSM
Sex workers
Sexually active
youth
Sexually active persons
Preventive
measure
Safe sex
Screening: STI
group, sex worker,
pregnant
Safe sex
Screening: STI
group, sex
worker
Safe sex
Screening: STI group, sex
worker, all sexually active
women aged 25 years or
younger
Vaccination
No
Disease
HPV
(Human Papillomavirus)
Causative agent
Virus
Reservoir
Humans
Mode of
Transmission
Sexual transmission
Vertical/ perinatal
transmission
Fomites
HSV
(Herpes Simplex Virus)
Sexual transmission
Vertical/ perinatal transmission
Contact with HSV in saliva or
genital secretions
Incubation period
2 - 3 months
2 - 12 days
Risk factors
Children
Sexually active young adults
Immunosuppressed patients
Neonates born to women with
genital HSV
Unprotected sexual intercourse
Preventive
measure
Safe sex : condom may
decrease risk
Safe sex
Health education and personal
hygiene
Cesarean section
Vaccination
Yes: Gardasil
No
Disease
HIV (Human Immonodeficiency Virus)/ AIDS (Acquired Immune
Deficiency)
Causative agent
Virus
Reservoir
Humans
Mode of
Transmission
Person to person


Unprotected sexual intercourse
Needle/ syringe sharing
Vertical transmission Breast feeding
Blood transfusion
Incubation period
Less than 1 month, Variable
Risk factors
Unprotected sexual intercourse
Injecting drug users
Sex workers
MSM
Health care workers
Preventive measure
Safe sex
Prevention of injecting drug use
HIV testing and counselling: high risk group
Postexposure prophylaxis
Preventing mother to child transmission




Universal HIV screening of pregnant women
Antiretrovirals
Elective cesarean section
Avoid breast feeding
Autologous transfusion
Universal precaution
Vaccination
No
Disease
HAV
HBV
HCV
Causative
agent
Virus
Reservoir
Humans
(Primary)
A-Anus
B-Baby/Booty/Blood
C-Cooker
Mode of
Transmission
Ingestion of fecally Perinatal/ vertical
contaminated food/ transmission
water
Percutaneous or mucosal
exposure to infective
body fluid
(Direct transmission)
Injection drug use
with sharing of
needles
(Indirect
transmission)
Receipt of blood/
Sexually transmission
(Direct transmission)
blood products from
unscreened donor
(Indirect
transmission)
Injection drug use with
sharing of needles
(Indirect transmission)
Incubation
period
28 - 30 days
60 -90 days (usually 45180 days)
2 weeks - 6 months
(6 - 9 weeks)
Risk factors
Living in/
travelling to high
endemic areas
Sexual partner or
household contact
Recipients of
unscreened donated
blood
MSM
Close personal
contact to patients
Preventive
measure
Vaccination
Injection drug users
Health care and public
safety work
Vaccination
Vaccination
Proper sanitation
Risk-based screening
Blood bank screening
test
Single use needle
Standard precaution
for blood
Yes
Yes
No
Disease
Dengue
Malaria
Causative agent
Virus
Protozoa parasites
Reservoir
Humans
Humans
Mosquito
Mosquito/ Apes(??)
Monkey
Monkey (P.knowlesi)(??)
Bite of infective mosquitoes
(day-biting species)
Bite of infective female mosquitoes
(night-biting species)
Mode of
Transmission
Incubation
period
3 -14 days
(commonly 4 -7 days)
PF: 9 - 14 days
PV & PO: 12 -18 days
(Some) PV: 6 - 12 months
PM: 18 - 40 days
Risk factors
Living in endemic areas
esp. children
Living in endemic areas
 universal except in human
with specific genetic traits
Perinatal transmission
Preventive
measure
Vaccination
Education
A - Aware of the risks
Prevention of bites from the
vector mosquito
B - Avoid being bitten by
mosquitoes
Vector control
 eliminate larval
habitats
C - Chemoprophylaxis
No
No
D - Immediate seek diagnosis and
treatment
Use ITN, LLIN, mosquito repellent.
Disease
Tuberculosis
Influenza
Causative agent
Bacterium
Virus
Reservoir
Humans
Aquatic birds
Bats
Influenza A - Pig, Horses, and
Seals
Humans
Mode of
Transmission
Infective droplet nuclei via
coughing or sneezing
Infective droplet nuclei via
coughing or sneezing
Incubation period
2 - 10 weeks
2 days
Risk factors
Exposure to active pulmonary
TB
All age group esp. extremely age
Compromised immunity
Extremely age
Obesity
Compromised immunity
Preventive
measure
Public education
Public education
BCG vaccine
Vaccination
Prompt diagnosis and treatment
Prophylaxis: anti-viral antigen
Infective control measure in
health care setting
Eliminate bovine tuberculosis
Vaccination
Yes
Disease
Leptospirosis
Causative agent
Bacterium
Reservoir
Renal tubule/ genital tract of wild and domestic animals
 rats
 swine
 cattle
 dogs
 raccoons
Mode of
Transmission
Contact of skin or mucous membranes with
 moist soil or vegetation contaminated with the urine of
infected animal (Indirect contact)
 contaminated water (Indirect contact)
 urine, fluids, or tissues of infected animals
Incubation period
5 -14 days (2 - 30 days)
Risk factors
Living in endemic area
Occupational workers
Yes
Preventive
measure
Public education
Protect workers in hazardous occupations
Control rodents and reservoir wildlife populations
Immunization of farm and pet animals/ people
Vaccination
Yes
Disease
Small pox
Anthrax
Causative agent
Virus
Bacterium
Reservoir
Humans
Herbivores, both livestock
and wildlife
Mode of
Transmission
Person-person via respiratory
droplets or skin inoculation
Transmitted from infected
animals to humans
Incubation period
7 - 19 days (10 - 14 days)
Cutaneous: 1 - 12 days (5 - 7
days)
Inhalation: 1 - 43 days
GI: 1 - 6 days
Injection: 1 -10 days
Risk factors
Preventive
measure
Unvaccinated persons
Occupational workers
Small pox research scientist
Heroin injection
Vaccination
Vaccination persons and
animals
Prevention and control in
animals
Vaccination
Yes
Yes
Disease
Ebola hemorrhagic fever
Causative agent
Virus
Reservoir
Forest/ cave-dwelling fruit bats
Mode of
Transmission
Person-person transmission occurs through direct contact with
infected body fluid
Nosocomial infection
Semen
Incubation period
5 - 15 days
Risk factors
All ages
People working with wildlife
Health care workers
Preventive measure
Strict procedures for isolation
Vaccination
No
Disease
Hantaviral diseases (HPS)
Causative agent
Virus
Reservoir
Deer mouse
Humans (accidental hosts)
Mode of Transmission Aerosol transmission from rodent excreta
Incubation period
2 weeks
Risk factors
Persons in rural populations who come into contact with rodents
Occupational workers
Health care workers
Preventive measure
Disinfection
Vaccination
Vaccination
Yes
9. Legionnaires’ Disease:
Pneumonia occurred in persons who attended conventions at a hotel on Broad
Street was legionnaire disease. The outbreak which occurred in the summer caused
182 cases, of which, 29 cases were fatal. Of the 182 legionnaire cases, 142 were
males and patientsʻ mean age was 54.7 years old. Mode of transmission was
airborne spread. There was no evidence of transmission from person to person,
food-borne, or water-borne. There was a consistency with the association of illness
with time spent in the lobby and on the sidewalk in front of the hotel, smoking habit
(patients are predominantly male), older age, and immunocompromised condition.
10. Bacterial STDs:
* Five leading National notifiable infectious disease 2012
US.
Hawaii
1. Chlamydia
1. Chlamydia
2. Gonorrhea
2. Gonorrhea
3. Salmonellosis
3. Salmonellosis
4. Syphilis
4. TB
5. HIV
5. Invasive pneumococcal disease
Age and Sex-
Chlamydia
Gonorrhea
Syphilis
Predominantly
Infection rate has
Predominantly male
specific Rates
Epidemiological
Trends
sexually active,
been decreasing
young female group both in the US and
(14-24 years).
Hawaii.
(MSM cases in HI:
74%) among middle
age (42 years in HI).
The prevalence (6.8
%) among female
14-24y is 3 times
higher than those
25-29 years).
In HI, more males
than females.
In US, proportion of
female cases has been
decreasing; but it is
increasing in HI (from
4% in early 2000s to
20% in late 2000s).
2.8 million
infections each
year.
Most infected
females are
asymptomatic;
most infected
males are
symptomatic.
Prevalence among
African American
has 5 times higher
than the rate
among nonHispanic white.
Among females,
mostly young age
groups (15y < 2024y> 30y).
Rapid spread of
drug resistance.
Racial and ethnic
group variations exist
(African American
population was 6
times higher than the
rate among nonHIspanic white
group).
Up to 70% of
infected females
and 50% of males
are asymptomatic.
Condom
Efficacy*
Can protect against
Chlamydia 90+%
Can protect
against Gonorrhea
90+%
Limited efficacy for
Syphilis protection
* Reference: Condoms and STDs: Fact Sheet for Public Health Personnel, CDC
11. Viral STDs:
Epidemiological
Trends
Incidence &
Prevalence
natural history
HPV
HSV
Most common STD in the U.S. ~
50-80% of sexually adults will be
infected at least once
Steadily trends in HPV-2
seroprevalence
Impact of HPV vaccine: Reduction
in HPV prevalence was found in
Seroprevalence: Overall
15.7%, increase with
increasing age
14-19 year old females
Most significant agent that cause
cervical and anal cancer
Prevalence among females
(survey): Overall 39.8%, Peak 2024 years
Infection usually goes away
completely by itself. Persistent
infection related to: older age, high
risk type, and infection with more
than one type.
Condom Efficacy
Most cases go
unrecognized and
undetected
It is because 80% of case
are
asymptomatic.
Recurrences are more
frequent within the first
few years but tend to
decrease over time
Condom use:
Limited efficacy
Hazard Ratio 0.3 for CSIL
Hazard Ratio 0.74
Hazard Ratio 0.0 for Intraepithelial for infection
lesions
* Gardasil vaccine: Quadrivalent vaccine which targets HPV type 6, 11, 16, 18. Responsible for
70% of cervical cancer (16 & 18) and 90% of external genital wart (6 & 11). RCT demonstrated
100% efficacy against HPV-related disease and 89% protection against HPV infection.
12. HIV/AIDS:
Descriptive
epidemiology
Risk
behavioral
groups
Globally/ Internationally
U.S.
Hawaii
35 million living with HIV
1.2 million
persons living
with HIV
Male 89%
Female 11%
New infection has been
decreased. However, HIV
incidence and HIV-related
mortality have increased in
Eastern Europe and Central
Asia driven by injection drug
use and needle sharing
Female 52%
Transmission: Predominantly
due to heterosexual sex
50,000 new
infections/year
(stable)
Male 80%
Female 20 %
Male:
80% MSM,
5% IDU,
6% MSM+IDU,
11%
Heterosexual
Transmission:
MSM 71%
IDU 8%
MSM+IDU 7%
Heterosexual
7%
Undetermined
6%
Transfusion
1%
Perinatal < 1%
Hemophilia <
1%
Female:
85%
heterosexual,
14% IDU
Africanamerican 47%
White 28%
Prevention
Caucasians
57%
Asians 15%
Hawaiians
11%
Hispanics 7%
Africanamerican 5%
Heterosexual transmission
 Condom
 Male circumcision
 Antiretroviral therapy for HIV-infected person
 Pre & Post exposure prophylaxis
General
 Testing of the blood supply
MSM



Condoms
Antiretroviral therapy for HIV-infected person
Pre & Post exposure prophylaxis
Mother to child transmission
 Antiretroviral therapy
 C-section
 Avoid breast feeding
Injection drug use
 Do not share equipment
 Syringe exchange programs
 Opiate substitution
 Pre & Post exposure prophylaxis
*PrEP:
Uninfected person takes HIV antiretrovirals, daily
May prevent replication of HIV infection
Candidates:
MSM
Transgender individuals
Heterosexual women and men - serodiscordant, multiple partners and
commercial sex workers
Injection drug users
13. Viral hepatitis:
Natural
history
HAV
HBV
HCV
2,700 new
infections in
U.S.
18,800 new infections in U.S.
up to 1.4 million chronic
infections (Most people do not
know they have it)
16,500 new infections
in U.S. up to 5 million
chronic infections
75 - 85 % of infected
adults will not resolve
Acute
infection only
Once resolved
-- lifelong
immunity
Possible chronic
Chronic infection
5% of infected adults
will develop to chronic stage.
90% of infected children will
develop to chronic stage.
Once resolved -- lifelong
immunity
Symptoms:
Acute:
Infant ~0%(Carrier)
child 10%(Carrier)
Adult 30%
Symptoms:
None ~80%
Treatment: up to 80%
cure
If resolve: no
protection
Highly infectious -stable in environment
for 4 days - 6 weeks
Treatment: no cure
Highly infectious -- stable in
environment for 7 days
14. Influenza:
Anti-genetic drift:
 Molecular changes in virus (small change)
 Occur constantly
Anti-genetic shift:
 The genetic change (major change) that enables a flu strain to jump from one
animal species to another, including humans (e.g., Swine flu, bird flu)
 Because people have no immunity, this can cause pandemic.
(Source: class handout of NIH )
Antigenic markers for influenza:


Three types - A , B , C
Flu strains based on surface antigen - Hemagglutinin (HA), Neuraminidase
(NA)
15.Dengue:
* Epidemiological triangle
 Environment:
 Rainfall, temperature, flight range, female density, feeding behavior
 Area and indoor spray, source reduction, genetic modification

Human:
 Movement, exposure, age, sex, urbanization, water storage practices
 Bug spray, long pants, screen windows/ bed nets

Virus: endemic or epidemic strain, mutation
*Antigenic markers
DENV 1-4
* Identify risk factors for DHF/DSS
 Children
 High viral load and elevated cytokines and chemokines are associated with
DHF
* Antibody dependent enhancement ( Immune enhancement) –
- once infected one strain of dengue virus, it will increase antibody and the
prior infection to heterogenous dengue increases a great risk. This causes the
problem on the vaccine developing processes because the vaccine has to be effective
for all strains of virus in order not to cause the immune enhancement issue.
*Epidemiological trend of occurrence
 Global resurgence (500-100 million annually, 75% is SEA and West Pacific)
16. Tuberculosis:
* Latent VS. Active TB
Latent TB (LTBI) (Goal = prevent future active disease)
= TB Infection
= No Disease
= NOT SICK
= NOT INFECTIOUS
Active TB (Goal = treat to cure, prevent transmission)
= TB Infection which has progressed to TB Disease = SICK (usually)
= INFECTIOUS if PULMONARY (usually)
= NOT INFECTIOUS if not PULMONARY (usually)
*Factors increased TB disease
Biomedical
 HIV infection* (strongest risk)
 DM
 Tobacco
 Malnutrition
 Silicosis
 Malignancy
Environmental
 Indoor air pollution
 Inadequate ventilation
Socioeconomic
 Overcrowding
 Urbanization
 Migration
 Poverty
 Population explosion
* Epidemiology of TB
Hawaii
Epidemiology # 1 in the
nation, but
improving
90% of TB
cases in
Hawaii are
foreign born
U.S.
Globally
1990 - TB
re-emerges,
co-infection
with HIV
After disappearing from the world
public health agenda in the 1960s
and 1970s, TB returned in the early
1990s for several reasons, including
the emergence of the HIV/AIDS
pandemic and increases in drug
resistance.
2010 Lowest # of
reported
cases in U.S.
*MDR-TB:


That is, strains resistant to isoniazid and rifampicin
This emerging problem was linked to
 improper prescribing practices,
 lack of patient adherence to treatment and irregular supply

low quality of drugs
17. Malaria:
P. Falciparum
Natural history
P. Vivax
Roughly Equal prevalence in
most of Asia and Central
America, where transmission is
low and seasonal.
Most
prevalence
P. Ovale
P. Malariae
Mainly in
subSaharan
Africa
Similar
distribution
with PV but is
rare
Second most
prevalence
Asexual cycle in blood: 48 h
Asexual cycle
in blood: 72 h
Some hepatic form remain
dormant as hypnozoites
for 2 weeks - more than a
year
Ass. general
seizures
Period of
communicability
(Untreated or
insufficiency treated
patients may be a
source of mosquito
infection)
< 1 year
up to 5 years
Several
decades
18. Leptospirosis:
*Epidemiology in Hawaii


Highest incidence rate in U.S.
 Kauai > Hawaii > Molokai
 Male > Female
A significant shift from peak occurrence during the drier summer months to
the wetter winter months


Highest age specific rate 20 - 29 years
Recreational > Occupational > Habitational
19. Smallpox and Anthrax
<Natural History>
Smallpox
Malaise, headache, rashes on extremity
Risk groups: caregiver, nursing person
Incubation period: 7-19 days (commonly 10-14 days)
Up to 4 days one can intervene after infected. Immunization after exposure
will significantly decrease. 20-50% case fatality rate.
Highly infectious, highly pathogenic, highly virulent.
Anthrax
Cutaneous (get lesion in cutaneous anthrax, don’t die from it)
Risk factors: slaughtering animals, close to herder.
disease (veterinarians, agriculture and wildlife worker in
developed country, persons working with animal hair or hide)
Incubation period: 5-7 days.
*Characteristics/ features that led the CDC to classify as “category A” bioweapon
agents
Feasibility of large-scale aerosol exposing
High infectivity among unvaccinated population
Bioweapons can be produced at low tech facility by independent groups.
9 points to remember regarding Anthrax (zoonotic bacteria – B. Anthracis,
spores)/ Small pox (variola virus)
1. Biological weapons: Small pox is more severe since it is difficult for Anthrax to
transmit via person to person
2. Both diseases can be prevented by vaccination.
3. Anthrax: Transmission- Cutaneous (most common but least severe) --- contacted
with infected animal, Gastro-intestinal --- consuming inadequately cooked
meat, Inhalation (most severe form, with > 85% of case mortality) --- risky in
industrial processes
4. Anthrax: Reservoir-herbivores/ spores, which contaminated soil, may remain
viable for year
5. Anthrax: Prevention-vaccinated high-risk persons and animals/ using proper
disinfected protocol for destroying B. Anthracis spores
6. Small pox: No known human cases since 1978, eradication was done primarily
by vaccination.
7. Small pox: Transmission: primary mode of infection is contact with infected
droplet.
8. Small pox: Reservoir-only human
9. Small pox: Prevention-vaccination with in 4 days of exposure prevents clinical
illness.
20. Ebola virus disease:
* Classified as a “Category A” (high-priority agent that poses a risk to national
security) bioweapon agent in 1999 by the CDC based upon:
 Potential to cause widespread illness and death
 Ease of dissemination or person-to-person spread
 (Only Ebola and Smallpox, not Anthrax)
 Potential for major public health impact
 Requirement for special public health preparedness
21.Hantavirus pulmonary syndrome:
* A case control study during the outbreak in the Southwestern U.S. found that these
factors were associated with risk of developing HPS:
 More small rodents at case household
 Hand plow
 Clean feed storage areas
 plants
 clean animal sheds
RESERVOIR OF INFECTION
1. Any person, animal, arthropod, plant, soil, or substance, or combination of these
in which an infectious agent normally lives and multiplies, on which it depends
primarily for survival, and where it reproduces itself in such a manner that it can be
transmitted to a susceptible host.
2. The natural habitat of the infectious agent.
Source: A Dictionary of Epidemiology (Kindle Locations 12197-12208). Oxford
University Press. Kindle Edition.