West Nile virus is a flavivirus of migratory birds named after the district in Uganda where it was first isolated in 1937. Migratory birds have probably been introducing the virus into the United States for decades, especially into New York City, which lies on the Atlantic flyway, one of the four primary migratory routes in North America. The virus can spill over from birds’ bodies into ours when mosquitoes bite infected birds and then bite people.
