BOX 13.
NEW INSIGHT INTO INFECTIOUS DISEASES:
AN EMERGING INTERFACE BETWEEN HEALTH AND THE ENVIRONMENT

In the early 1960s, Machupo virus, a new pathogen transmitted directly from rodents to humans, ultimately infected over one-third of the population of San Joaquin, Bolivia, and killed hundreds before it subsided.

Considered endemic to developing countries, Machupo virus and its sister pathogens remained more or less unstudied until 1993, when an outbreak of the related Hantavirus Cardio-Pulmonary Syndrome occurred in the Southwestern United States (Parmenter et al. 1993).

Hantaviruses are a group of RNA viruses, many of which are highly pathogenic to humans (Keller et al. 1998). This new virus was found to use the deer mouse as its primary reservoir and to be fatal in almost 50 percent of human cases. Since this discovery, almost 30 new Hantaviruses have been found in the New World, half of which are known to be pathogenic to humans (Hjelle et al. 1995). The specific origins of these new viruses and the cause of the 1993 outbreak appear to be due to a complex set of evolutionary and ecological factors. For example, El Ni&#ntilde;o events are now known to trigger population explosions of host rodent populations and eventually an increased incidence of infection in mice—and increased risk of infection in humans. Data from NSF-supported long-term ecological and biodiversity research have played a significant role in our growing understanding of these emerging viruses. This new understanding, improved remote-sensing capabilities, and modeling of complex systems are enabling improved prediction and prevention of Hantavirus outbreaks in the Western United States.

This understanding and other similar studies have led to a fundamental change in how we approach the study of diseases and is leading to the emergence of a field of study in the ecology of infectious diseases (Anderson and May 1991, Dobson and Carpenter 1996, Real 1996). These studies are multidisciplinary by design and require long-term data to be robust (Parmenter et al. 1999). They hold great potential for allowing the development of predictive models, not just for Hantaviruses, but for many other diseases. A clear understanding of the ecology and evolution of these pathogens will be needed if we are to respond effectively to emerging biological threats.