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Farr's law applied to AIDS projections
1Department of Preventive Medicine, University of Southern California, Los Angeles 90033.
JAMA
|March 16, 1990
Summary
Farr's Law accurately models epidemic curves. Applying it to acquired immunodeficiency syndrome (AIDS) in the US shows a projected 200,000 cases, with a decline by the mid-1990s.
Area of Science:
- Epidemiology
- Public Health
- Biostatistics
Background:
- Farr's Law of Epidemics, proposed in 1840, describes epidemic rise and fall using a normal distribution.
- Previous research by Brownlee in the early 1900s supported this law.
- Understanding epidemic patterns is crucial for public health interventions.
Purpose of the Study:
- To assess the applicability of Farr's Law to the acquired immunodeficiency syndrome (AIDS) epidemic in the United States.
- To project the trajectory and potential size of the early AIDS epidemic using epidemiological data.
Main Methods:
- Analysis of reported annual incidence of AIDS cases in the US from 1982 to 1987.
- Application of normal distribution (bell-shaped curve) approximation based on Farr's Law.
- Statistical modeling to forecast epidemic crest and decline.
Main Results:
- The 6-year AIDS incidence data closely fit a normal distribution.
- The epidemic's peak was projected for late 1988.
- A decline to low incidence levels was predicted by the mid-1990s, with an estimated 200,000 total cases.
Conclusions:
- Farr's Law provides a valid model for the early United States AIDS epidemic.
- The epidemic was predicted to follow a symmetrical rise and fall pattern.
- A low level of endemic cases is expected to persist after the epidemic peak.
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