Epidemiology & Public Health

Basic

Prevalence

Proportion of a population that has a particular condition at a point in time.

Formula

P = \frac{\text{Existing Cases}}{\text{Total Population}} \times k

Variables

PPrevalence

\text{Existing Cases}All current cases

\text{Total Population}Entire population

kMultiplier

Example

1 500 cases in 300 000 people → 500 per 100 000

Did You Know?

A disease with a long duration will have high prevalence even if its incidence is low — diabetes is a classic example.

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More in Epidemiology & Public Health

Incidence Rate

Rate at which new cases of a disease appear in a population over a given period.

Basic Reproduction Number

Average number of secondary infections produced by one infected individual in a fully susceptible population.

Herd-Immunity Threshold

Minimum fraction of the population that must be immune to prevent sustained spread.

Effective Reproduction Number

Actual average infections per case when part of the population is already immune.

SIR Model — Susceptible

Rate of change of the susceptible population in the SIR compartmental model.

SIR Model — Infected

Rate of change of the infected population — new infections minus recoveries.