West Nile Virus and the Southeast's Mosquito Seasons

West Nile virus is the leading cause of domestically acquired arboviral disease in the continental United States. It is maintained in a cycle between birds and Culex mosquitoes, with humans as incidental hosts.

Most infections are silent. About 80% of people who are infected have no symptoms at all, and most of the rest develop a self-limited febrile illness. Fewer than 1% go on to neuroinvasive disease such as meningitis or encephalitis, which can be severe or fatal, especially in older adults.

There is no specific antiviral treatment and no human vaccine, so prevention is everything: insect repellent, protective clothing, and reducing standing water where mosquitoes breed.

In the Southeast, activity peaks in the warm months. A summer or fall febrile illness with neurologic signs should prompt consideration of West Nile.