Infectious Diseases Flashcards
Define outbreak
= Localized disease epidemic (e.g., in a town or healthcare facility)
Define pandemic
an epidemic on a worldwide scale (e.g., 1918 flu)
Define epidemic
Excessive occurrence of disease (vs. usual frequency)
Define communicable/infectious disease
= Illness caused by infectious agent that can be transmitted from one person to another (what do we mean by transmitted?)
Define epidemic threshold
minimum number of cases (or deaths) that would support the conclusion than an epidemic was underway, based on statistical projections and expectations of usual frequency
NEED DATA ON USUAL OCCURRENCE OF DISEASE TO KNOW IF IT’S AN EPIDEMIC
Yes…
Define agent
the cause of the disease
define host
an organism, usually a human or animal that harbors a disease
define environment
is those surroundings and conditions external to the human or animal that cause or allow disease transmission
What are three major factors in the pathogenesis of disease, FUNDAMENTAL PUBLIC HEALTH CONCEPTION OF DISEASE CAUSALITY
well-suited to explaining etiology of infectious disease; ALSO IMPORTANT FOR UNDERSTANDING METHODS FOR INVESTIGATION AND CONTROL OF EPIDEMICS
Diseases do not occur in a vacuum, virtually all result from some interaction between host, agent and environment.
And even though some diseases are genetic in nature, even the presentation of these depends on interaction between genetic and environmental conditions.
Many of the underlying principles re: disease transmission are most clearly demonstrated using infectious disease model
Shows the interaction and interdependence of agent, host, environment, and time as used in the investigation of diseases and epidemics.
What is pathogenicity and high low
high pathogenicity means it causes disease in almost everybody, low it causes a disease but it doesn’t impact you as much, most people have subclinical levels, you can be affected by it but it doesn’t show, you are exposed to polio but you won’t get it.
-Capacity of the agent to cause overt disease in the infected host
-High pathogenicity (few subclinical cases): measles
-Low pathogenicity (most cases are subclinical): polio
= number of individuals with clinically apparent disease / number exposed to an infection
what CHARACTERISTICS INFLUENCE WHEN AN INFECTIOUS DISEASE AGENT WILL BE TRANSMITTED TO A AHOST, WHETHER ITWILL PRODUCE DISEASE, THE SEVERITY OF DISEASE AND THE OUTCOME OF INFECTION?
- toxigenicity
- resistance
- antigenicity
Define resistance
-ability of agent to survive adverse environmental conditions. The flu: conditions need to be exactly right for the flue to exists, anthrax is highly resistant bc they can be in the ground for years, hepatitis
Define toxigenicity
the ability of the agent to produce a toxin or poison
ex: shellfish poisoning
Define antigenicity
- the ability of an agent to produce antibody production in a host, a disease with high antigenicity is a disease that you get and you are not worried about getting again because it caused a high antibody reaction in the body
- Related to immunogenicity = infection’s ability to produce specific immunity
- Some agents induce long-term immunity against infection, e.g., reinfection with measles is rare
Define infectivity and give examples
-what do i need to do in order to transmit a disease, how easy is it to transmit a disease
-Capacity of an agent to enter and multiply in a susceptible host and produce infection or disease
-Measured by the secondary attack rate
Ex: polio and measles have high infectivity rate
