West Nile Virus Information

West Nile is a type of virus that causes encephalitis or inflammation of the brain.  The virus has occurred in Africa, Western Asia, the Middle East, the Mediterranean region of Europe and recently in the United States.

Mosquitoes become infected with the virus after feeding on infected wild birds and then transmit the virus through bites to people, animals and other birds.  The American Crow appears to be the most severely affected, but WNV has also been found in other domestic birds including doves, sea gulls, robins, blue jays, hawks, herons, and eagles.  Birds serve as the reservoir hosts of WNV, and the principal vector in the transmission from one bird to another is the Culex mosquitoes.  WNV has also been found in several species of Aedes mosquitoes, which could serve as bridge vectors by transmitting it to humans or horses.

Most infections produce no symptoms in people, or symptoms are mild or moderate.  Symptoms may include: fever, headache, sore throat, fatigue and body aches, often with skin rash and swollen lymph glands. More severe infections may be marked by headache, high fever, neck stiffness, muscle weakness, stupor, disorientation, convulsions, paralysis, coma, and rarely, death.

There is no specific therapy.  In more severe cases, intensive supportive therapy is indicated;  that is, hospitalization , intravenous fluids, airway management, respiratory support (ventilator) if needed, prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

Symptoms usually appear 5 to 15 days from the time a mosquito carrying WNV infects a person.

Since the majority of infected persons are asymptomatic, the fatality rates is less than 1%.  However, case  fatality rates for hospitalized patients is around 5%, and are highest in the elderly.

West Nile virus infects certain wild birds. Crows, jays, ravens, and magpies tend to become sick and die from infection. Increasing numbers of dead birds may be an indication of West Nile virus in your community. You can help by reporting dead crows and other birds to your local Mosquito Control Office. Use gloves or double plastic bags to place the carcass in a garbage can.