U.S. Department of Commerce


Date of this Version



Published in Science, New Series, Vol. 288, No. 5475 (Jun. 30, 2000), pp. 2319-2320.


P. Daszak, A. A. Cunningham, and A. D. Hyatt present a convincing argument in their Review "Emerging infectious diseases of wildlife-threats to biodiversity and human health" (Science's Compass, 21 Jan., p. 443) that emerging infectious diseases (EIDs) pose a risk to wildlife, and they suggest that EIDs most often result from a change in the ecology of the pathogen or the host (or both). A situation they did not mention is that in some cases, the protection of threatened species can increase the risk of an EID outbreak by allowing a close association between wildlife and domestic animals where one would not have naturally occurred. An important example is northern elephant seals (Mirounga angustirostris) (see figure at left), which were abundant in, California and Baja California, Mexico, at the beginning of the 19th century before being nearly eliminated by hunting. During the population bottleneck that resulted, there may have been fewer than 100 seals until some- time after 1900 (1). However, during the 20th century, this species made a remarkable recovery. In 1991, the population was estimated to be 127,000 (2).