Pathogen survival in the external environment and the evolution of virulence.

Recent studies have provided evolutionary explanations for much of the variation in mortality among human infectious diseases. One gap in this knowledge concerns respiratory tract pathogens transmitted from person to person by direct contact or through environmental contamination. The sit-and-wait hypothesis predicts that virulence should be positively correlated with durability in the external environment because high durability reduces the dependence of transmission on host mobility. Reviewing the epidemiological and medical literature, we confirm this prediction for respiratory tract pathogens of humans. Biol Rev. 2004;(79):849-69.