Infectious Disease Epidemiology Flashcards
“any deviation from or interruption of the normal structure or function of any part, organ, or system (or combination thereof) of the body that is manifested by a characteristic set of symptoms and signs . . .”.
disease
“a state of optimal physical, mental, and social well-being, and not merely the absence of disease and infirmity.”
Health
an illness due to a specific infectious (biological) agent or its toxic products capable of being directly or indirectly transmitted
communicable (infectious) disease
transmitted through contact.
contagious disease
t/f All contagious diseases are communicable
true
Not all communicable diseases are contagious
dengue
Some diseases are both communicable and contagious
measles
the person, animal, object or substance from which an infectious agent passes or is disseminated to the host (immediate source).
Source of infection
any person, animal, arthropod, plant, soil, or substance, or a 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. It is the natural habitat of the infectious agent.”
Reservoir
infection that is transmissible under natural conditions from vertebrate animals to man
Zoonosis
rabies, plague, bovine tuberculosis…..
a person in the population or study group identified as having the particular disease, health disorder, or condition under investigation
case
Person who brings the disease/infection into a population
Primary Case
Persons who are infected by primary case
Secondary case
First case discovered during an outbreak
Index case
infected person or animal that harbors a specific infectious agent in the absence of discernible (visible) clinical disease and serves as a potential source of infection to others.
CArrier
Three elements have to occur to form a carrier state
The presence in the body of the disease agent.
The absence of recognizable symptoms and signs of disease.
The shedding of disease agent in the discharge or excretions.
An insect or any living carrier that transports an infectious agent from an infected individual or its wastes to a susceptible individual or its food or immediate surroundings.
VECTOR of INFECTION
An infectious agent seeks a susceptible host aiming “successful parasitism
Susceptible host
Four stages are required for successful parasitism:
Portal of entry
Site of election inside the body
Portal of exit
Survival in external environment
Features unique to infectious diseases:
- A case may also be a source.
- People may be immune.
- A case may be a source without being recognized.
- There is often a need for urgency.
- Preventive measures often have good scientific basis.
Outcomes of exposure
- No infection
- Clinical infection resulting in death, immunity, carrier or non-immunity
- Sub-clinical infection resulting in immunity, carrier or non-immunity
- Carrier
entry and development or multiplication of an infectious agent in the body of man or animals.
INFECTION
time from exposure to development of disease. In other words, the time interval between invasion by an infectious agent and the appearance of the first sign or symptom of the disease in question.
Incubation period
the period between exposure and the onset of infectiousness (this may be shorter or longer than the incubation period).
Latent Period
Length of time a person can transmit the disease (sheds the infectious agent)
Infectious period
This is infection by organisms that take the opportunity provided by a defect in host defense (e.g. immunity) to infect the host and thus cause disease.
Opportunistic infection
The presence of an infectious agent on a body surface, on or in clothes, beddings, toys, surgical instruments or dressings, or other articles or substances including water and food
contamination
It is the lodgment, development and reproduction of arthropods on the surface of the body or in the clothing, e.g. lice, itch mite. This term could be also used to describe the invasion of the gut by parasitic worms, e.g. ascariasis.
Infestation
is an infection originating in a patient while in a hospital or another health care facility
Nosocomial (hospital acquired) infection
The way the disease progresses in the absence of medical or public health intervention
Natural History of Disease
BIOLOGIC SPECTRUM OF DISEASE
ICEBERG PHENOMENON
Studying only symptomatic individuals may produce misleading
ICEBERG PHENOMENON
a host characteristic that can limit the ability of an infectious agent to produce infection
Immunity
resistance of a group of people to an attack by a disease to which a large proportion of the members of the group are immune.
Herd immunity
The unusual occurrence in a community of disease, specific health related behavior, or other health related events clearly in excess of expected occurrence”
Epidemic
It refers to the constant presence of a disease or infectious agent within a given geographic area or population group. It is the usual or expected frequency of disease within a population.
Endemic
