West Nile Virus

West Nile virus (WNV) is a disease mostly affecting birds. It is spread among birds by mosquitoes. Mosquitoes get the virus from biting infected birds and then can pass it on to other birds, animals, or people. These mosquitoes can sometimes bite a person, but most people do not become very sick. In some people, West Nile Virus can cause encephalitis, or swelling of the brain.

WNV was first detected in the US in 1999 and has quickly spread across the country. It was detected first in Oregon in 2004 in the southeastern county of Malheur. In Multnomah County, the first case of West Nile was found in 2006 in a bird in southeast Portland. Three additional cases were discovered last year, two in northeast Portland and one in Gresham. There have been 16 WNV cases, all in birds, so far in 2007 (see map for locations).

Page updated March 06, 2008