West Nile Virus (WNV)
West Nile Virus (WNV)
West Nile virus (WNV) is a mosquito-transmitted virus that can cause encephalitis (inflammation of the brain) in some people. This virus usually circulates between mosquitoes and birds in Africa and Europe. However, in 1999, an outbreak of West Nile encephalitis was reported in New York City. Since then, the virus has spread to 48 states and the District of Columbia.
In July 2002, WNV was found in Minnesota. Fortunately, most people who are bitten by infected mosquitoes will experience either no symptoms, or mild illness.
West Nile Virus F.A.Q.
West Nile encephalitis is a viral disease transmitted to people and horses through the bite of an infected mosquito.
West Nile virus (WNV) is maintained in a transmission cycle involving one or more species of mosquitoes and birds. Current research is focusing on which mosquitoes and birds are most important in this cycle.
WNV is usually found in Africa and southern Europe. The virus was first reported in North America during a 1999 outbreak of encephalitis in New York City.
How serious is West Nile virus?
Most people infected with WNV will have either no symptoms or a very mild illness. A small percentage of people, especially elderly patients, may develop encephalitis (inflammation of the brain). Approximately 10% of these encephalitis cases are fatal.
Most of the severe human cases of WN encephalitis begin with sudden onset of fever, headache, stiff neck, and vomiting. The illness progresses quickly to include confusion and other mental status changes, altered reflexes, convulsions, and coma. There is no treatment for WN encephalitis other than supportive care.
Approximately 33% of symptomatic horses are put down or die from WNV infections.
What can people do to prevent West Nile Encephalitis?
Personal protection measures such as use of mosquito repellents, avoiding outdoor exposures at dusk and dawn (peak feeding time for many mosquitoes), and wearing long-sleeved shirts and long pants can reduce the risk of WN encephalitis.
Removal of water-holding containers (mosquito breeding sites) from residential areas will reduce numbers of several mosquito species.
There is a vaccine available for horses to prevent WN encephalitis. Please contact your veterinarian for vaccine recommendations. A human WNV vaccine is still in development.