West Nile Virus - 8 of 15
West Nile Virus FAQs - 15 Found
Since West Nile Virus (WNV) was not detected in the Western Hemisphere until 1999, native bird populations in the U.S. were not previously exposed to the virus. It is not unusual for a new disease to cause high rates of infection or death in a population that does not have natural immunity to the infection. We don’t know if or how long it will take for bird populations to develop sufficient immunity to West Nile Virus. Surveys of wild birds have shown that some birds already have antibodies to WNV. Most bird testing and surveillance programs for WNV in the U.S. have been focused only on testing for the presence of the virus in the birds. Testing for other possible causes of death was not being conducted, so it is unknown if all of the bird deaths are due to West Nile Virus infection.