October 27, 2001
Mathematical modeling is about rationally predicting the future based on data from today. Mathematical modeling is always a simplification and an abstraction of reality, but that simplification allows you to identify critical steps and their relative importance in predicting what is going to happen.
Blower has written important papers about mathematical modeling and the HIV epidemic in San Francisco. In 2000 he published an important article in Science. Using mathematical modeling of the HIV epidemic in San Francisco, he suggested that widespread treatment of HIV might reduce the rate of transmission by reducing the viral load of a given population. His group also predicted that an increase in risk behavior of only 10% would result in an increase in the incidence rate of HIV infection. Unfortunately, that is exactly what has happened. The widespread availability of an effective treatment, and the perception that AIDS is a controllable disease has changed the sexual behavior of large segments of the population, increased high risk practices and resulted in a new wave of infections.
In this abstract, Blower tackled a different problem -- the transmission of drug-resistant strains in the San Francisco community. He mathematically modeled the transmission potential of 1,000 different drug-resistant strains for the years 1995 to 2005. His conclusion was that although the current prevalence of drug resistance is high (29%), most of it is due to the acquisition of resistance during treatment and not because of the acquisition of resistant strains. The transmission of resistant strains will remain low. The main problem is not the acquisition of resistant strains, but the transmission of sensitive ones. New cases of HIV have gone up. Public health efforts should focus on trying to prevent new infections, rather than worrying too much about resistant strains.
By the way, the authors have recently published the papers that lead to this abstract in Nature Medicine. If you like modeling, it is worth reading. The full reference is: S.M. Blower, A.N. Aschenbach, H.B. Gershengorn, J.O. Kahn. Nature Medicine 7, 1016-1020 (September 2001).
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