Emerging infections: lessons from the viral hemorrhagic fevers.

Two Institute of Medicine reports since 1992 have emphasized the dangerous and continuing threat to the world from emerging infectious diseases. Working with viral hemorrhagic fevers provides a number of lessons related to the processes that control emergence, the pattern of disease after emergence, and how to cope with these incidents. This short paper uses two arenavirus hemorrhagic fevers to illustrate some of these principles. Argentine and Bolivian hemorrhagic fevers first came to medical attention in the 1950's. The forces that underlie the emergence of disease in Argentina are not understood, but the Bolivian episode has a reasonably understandable train of events behind it. The Argentine disease had serious impact on the large agricultural economy, and the ecology of the rodent reservoir did not lend itself to control; a vaccine was developed by Argentina and the U.S. with the latter motivated largely by biodefense. The Bolivian disease was controlled in large part by eliminating rodents that invaded towns, and the impact was subsequently below the level needed to trigger drug or vaccine development. These two viruses were important in the recognition of a new family of viruses (Arenaviridae), and this finding of new taxons during the investigation of emerging infectious diseases continues.