Ecological Monitoring Helps Researchers Study Disease in Environmental Context

WHEN a previously unknown and deadly respiratory illness appeared in 1993 in the American Southwest, the outbreak sent researchers scrambling to learn the cause of the infection—a previously unknown Hantavirus—and to discover just why the new disease surfaced so dramatically at that time and place.

Thanks to the availability of records of local climate conditions as well as data for the population levels of deer mice found to be the vector for the infection, scientists constructed a plausible scenario that most felt was the likely explanation for the disease's emergence.

Six years of drought, followed by extremely heavy rains in the spring of 1993—rains thought to be related to the El Niño pattern of warming in parts of the Pacific Ocean—had caused a bumper crop of piñon nuts and a 10-fold surge in the numbers of well-fed deer mice. Case-control studies revealed that contact with rodent feces through agricultural