The outbreak of West Nile virus in the United States is rapidly becoming a significant threat to public health. With the peak season just beginning, the mosquito-borne virus has been found in animals (primarily birds and horses) in 38 states, and has caused 103 serious infections and three deaths in humans in 15 states. Last year, there were more than 4,000 cases and almost 300 deaths. We may be on the verge of an epidemic, but there is no treatment and a vaccine is at least a decade away.

Public health officials have recognized the seriousness of the problem, but too often their response has been tepid and designed to avoid controversy. The Centers for Disease Control Web site, for example, advises people to avoid mosquito bites by covering up, using insect repellent, and staying indoors during peak mosquito hours. Missing from its list of suggestions, however, is any mention of insecticides or widespread spraying. Anyone curious about the role of pesticides in battling mosquitoes and West Nile is directed to a maze of other Web sites.

In the absence of a vaccine, elimination of the organism that spreads the West Nile virus — in this case, the mosquito — is the key to prevention, but fundamental shortcomings in public policy limit the tools that are available...