Markers of Disease Evolution: The Case of Tuberculosis

Abrupt changes in environmental conditions—broadly understood to include demographic and social dynamics—can seriously impact the local or global disease dynamics of a population. These changes in the evolutionary landscape, which may occur over relatively short time-scales, are very likely to play a critical role in disease evolution. The potential impact of demographic, social and epidemiological shifts on the evolution of tuberculosis epidemics in the United States over the past century and a half is the main subject of this article. Evidence is provided to support the hypothesis that the observed substantial decreases in the incidence of active tuberculosis are the result of abrupt reductions in the rates of disease progression.