Wednesday, November 13, 2013

SOME EPIDEMIOLOGICAL TERMS

Incidence is a number equal to the fraction of population that contracts a given disease during a given period of time. In other words, Incidence is the rate at which new cases of diseases occur within a population.

Prevalence of a disease is the fraction of the population that currently (or at some other particular time) has a given disease.

A sporadic disease is one that occurs only occasionally in a population (i.e., prevalence is zero).

An endemic disease is one that is always present in a population (i.e., never zero prevalence).

An epidemic disease is a disease that many people acquire over a short period (i.e., increasing incidence).

A pandemic disease is a world-wide epidemic disease (i.e., high world-wide incidence).

Common source outbreaks are some diseases arise from a single definable source, such as a common water supply. They are not propagated from individual-to-individual (e.g., person-to-person). Yet the disease continues to be endemic and perhaps epidemic as a consequence of contact with some typically geographically well-defined disease reservoir

Propagated epidemics are in contract, which are diseases spread not from some common, geographically well defined disease reservoir, but instead by individual-to-individual (e.g., person-to-person) contact.

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