Two years ago, Mother Nature one-upped an Institute of Medicine (IOM) committee big time. In 1991, the committee had wracked its collective brains to come up with a plausible epidemic scenario for a report on disease emergence. The team finally settled on a potential southern US outbreak of yellow fever, a well-known African viral disease carried by mosquitoes. The idea was realistic, if not particularly imaginative. Yellow fever is an old problem. Shortly after the report on microbe-induced epidemics was released, Mother Nature displayed tremendous creativity. In the spring of 1993, a mysterious virus began killing young people in the Southwest. The culprit turned out to be a previously unrecognized strain of hantavirus, which causes a deadly respiratory disease. Emerging from its natural host, the common deer mouse, the hantavirus strain affected at least 131 people. Half died. Today, emerging viruses have shocked the public and sent scientists searching for causes of epidemics and factors that determine how serious disease outbreaks might be be. One factor gaining attention climate. To learn how global warming might affect mosquitoes, mice and other microbe carriers, biologists are studying diseases within an environmental context. This article discusses the work in this area and somemore » of the results, speculations, and future areas of interest.« less