West Nile Virus Encephalitis

Normally seen in the Middle East and some parts of Europe and Asia, the WEST NILE VIRUS can cause ENCEPHALITIS in some people. The first outbreak of West Nile Virus encephalitis occurred in 1999 in the Western hemisphere. There were a total of 62 cases of human encephalitis or MENINGITIS and seven fatalities in New York City and adjacent Long Island and Westchester County. In addition, mosquitoes and more than 20 bird species were found to be infected with West Nile virus in New Jersey, Connecticut, New York state, and Maryland. In the hardest hit section of Queens, 2.5 percent of humans tested were found to have been infected with West Nile virus. Fatal infection was also seen in horses on Long Island.

The future impact of West Nile virus is uncertain. States on the eastern bird flyway have received federal funding to conduct monitoring activities and perform diagnostic assays. This effort will be expanded nationwide. While all residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis, people over age 50 are at highest risk of severe disease.

Cause
The virus, which normally circulates in birds and mosquitoes, crosses to humans who are bitten by an infected mosquito. The virus then multiplies in the person’s blood and eventually crosses the bloodbrain barrier to reach the brain. At this point, the virus interferes with normal central nervous system functioning and inflames brain tissue.

Symptoms
Most human illness from West Nile infection is mild, but severe disease is more common in the very young and very old, or those people with a weakened immune system. From three to 15 days after infection, symptoms may appear including fever, headache, and body aches, occasionally with skin rash and swollen lymph glands. More severe infection may be marked by headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, paralysis, and, rarely, death.

Less than 1 percent of those infected with West Nile virus will develop severe illness; of those who do, between 3 percent and 15 percent will die.

Diagnosis
Patients who are at high risk and who have symptoms of West Nile encephalitis will have a sample of their blood sent to a lab to confirm the diagnosis.

Treatment
Treatment is supportive for the encephalitis or meningitis associated with the infection. Severely ill patients may be hospitalized and given intravenous fluids, airway management, a ventilator, and perhaps antibiotics to prevent secondary infection.