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West Nile Virus


West Nile virus was first isolated in Uganda in 1937. Today it is most often found in Africa, Eastern Europe, the Middle East, and West Asia. In 1999, the virus appeared in North America for the first time, and the following year the virus was reported in 12 states along the East coast. In the two years since West Nile virus was first reported in the United States, it has killed eight people and sickened 80 others.

West Nile virus is a member of the flavivirus group, viruses spread by insects and known to cause disease in humans and animals. In the United States, birds appear to be the major carrier of the disease. When certain mosquito species feed on the blood of infected birds, the insects ingest the virus. When these mosquitoes bite people, they can pass the virus into humans.

Most people infected with West Nile virus have only mild illness. In the worst cases, however, the virus causes encephalitis, an inflammation of the brain. No specific medication exists to treat West Nile virus infection, and no vaccine is available to prevent it.

NIAID Research

Vaccine Research

Acambis, a company in Cambridge, Mass., has developed a West Nile virus vaccine based on an existing vaccine that protects against yellow fever. Thomas Monath, M.D., heads a fast-track project to replace parts of the yellow fever vaccine with proteins from the West Nile virus and test this construct in animals. Trials in mice have shown promising results, and the results of additional testing in horses are expected by early summer. The company expects clinical trials to begin in humans by late 2002.

Drug Research

John Morrey, Ph.D., of Utah State University's Institute for Antiviral Research in Logan, has developed a system for screening large numbers of drug candidates for their potential efficacy against West Nile virus. Dr. Morrey used the New York strain of the virus in his studies,making any drugs discovered applicable for use in the United States. He also uses the well-established Uganda strain to show that the efficacy of active materials is not limited to just this one virus strain. Molecules that show initial effectiveness against the virus will be selected for further study and development.

Focus on Mosquitoes

Dov Borovsky, Ph.D., of Insect Biotechnology, Inc. (Redwood City, Calif.) and Brian Federici, Ph.D., of the University of California at Riverside, are working on new ways to destroy mosquito larvae. Dr. Borovsky is scheduled to begin initial field trials, closely monitored by NIAID and the Environmental Protection Agency, of a novel larvicide based on a naturally occurring peptide (short protein) that causes mosquito larvae to starve to death. Dr. Federici has begun to develop a combination of larvicidal bacterial peptides that he hopes will prevent resistance to any single individual agent.

Under an NIAID International Collaboration in Infectious Disease Research, Colorado State University's Barry Beaty, Ph.D., and Dr. Jose Farfan of Universidad Autonoma de Yucatan in Mexico study the trafficking potential of West Nile virus into Central and South America. More than 1,200 migratory and resident birds have now been captured, sampled, and released. Blood samples are currently being processed to look for evidence of West Nile virus or other flavivirus infections.

Additional links:

CDC backgrounder on West Nile virus
CDC backgrounder on arthropod-borne encephalitis viruses
Maps showing West Nile virus surveillance in the United States
Mosquito control information from the Environmental Protection Agency
USDA summary of West Nile virus in the United States
USGS information on West Nile virus