Daily News Archive
From April 12, 2001

CDC Announces New Guidelines for Combating the West Nile Virus

On April 12, 2001, the Centers for Disease Control and Prevention (CDC), Division of Vector-Borne Infectious Diseases, released Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for Surveillance, Prevention and Control. CDC originally released guidelines for the 2000 West Nile virus season, but updated its recommendations following a workshop held in Charlotte, North Carolina earlier this year.

The revised guidelines provide recommendations and goals for surveillance of mosquitoes, birds, equines and humans, as well as the advantages and disadvantages noted from two years of experience. According to the report, because the primary objective surveillance systems is to prevent human cases, CDC recommends that human surveillance be used only when arbovirus activity is considered to be unlikely, or if resources are not available for avian or mosquito-based arbovirus surveillance.

In terms of control, CDC recommends a program that includes surveillance, source reduction, chemical (pesticide) control, resistance management, biological control (fish, nematodes), technical education, and public education and outreach. According to CDC, pesticides should be used "when source reduction and water management are not feasible, or have failed because of unavoidable or unanticipated problems…" or "to prevent disease when surveillance indicates the presence of infected adult mosquitoes poses a risk to human health."

The report goes on to say that pesticides can be directed against adults or immature mosquitoes, although larvicides, both conventional and biologically-based, are typically more effective. CDC states that adulticides (pesticides used to kill adult mosquitoes), while the least effective, are "an extremely important part of an integrated mosquito management program." According to the revised guidelines, based on surveillance, adulticides may be used at risk category #2, which is defined as, "Probability of human outbreak low; spring, fall or summer; areas with initial, sporadic or limited West Nile virus epizootic activity in birds or mosquitoes.

The CDC report is available at www.cdc.gov/ncidod/dvbid/westnile/resources/wnv-guidelines-apr-2001.pdf.