West Nile Virus Cases Reported in Multiple U.S. States This Year

Health officials have confirmed human cases of West Nile virus in several states this year. Tennessee and Texas reported infections, while California detected the virus in two mosquito samples and four dead birds by mid-May 2026. Warmer temperatures have contributed to an early increase in mosquito populations. The virus spreads primarily through bites from infected Culex mosquitoes.

Mosquitoes acquire the virus after feeding on infected birds and can then pass it to humans, horses, and other mammals. No approved vaccine or specific antiviral treatment exists for the disease. West Nile virus was first identified in Uganda in 1937 and first detected in the United States in New York in 1999. Since then, more than 51,000 symptomatic cases have been reported nationwide.

The Centers for Disease Control and Prevention map shows human, bird, or mosquito cases in nearly every state except Alaska, Hawaii, New Hampshire, and Vermont. Mosquitoes have also been documented in Iceland for the first time last October. The CDC recommends using EPA-approved repellents, wearing long sleeves and pants at night, and eliminating standing water around homes.

Travelers to parts of Asia and the Americas are advised to consult physicians before departure.