Map Shows Mosquito-Borne West Nile Virus Spreading Across US, Killing Eight

The mosquito-borne West Nile virus is spreading across the United States, with 222 human cases reported as of August 18, according to the U.S. Centers for Disease Control and Prevention (CDC). Of these, 156 cases are neuroinvasive, the most severe form that can affect the brain and nervous system. The virus is also detected in mosquitoes, birds, and other animals, indicating its widespread circulation beyond human-affected areas.

Eight deaths have been reported this season, with five in Arizona and three in California. Arizona has reported the most cases at 76, followed by Texas with 31 and California with 29. However, 18 states currently have no reported cases, including those in the Midwest, Mid-Atlantic, Northeast, Alaska, and Hawaii.

There is no vaccine or specific antiviral treatment for the general public. Prevention focuses on avoiding mosquito bites through EPA-registered insect repellents, wearing long-sleeved clothing, and ensuring screens on windows and doors are intact. Eliminating standing water around homes can also reduce mosquito breeding grounds.

Most infected individuals show no symptoms, but 20 percent develop mild West Nile fever, characterized by fever, headache, and body aches. A small percentage progress to severe neuroinvasive disease, which can cause high fever, confusion, and paralysis, with a fatality rate of about 10 percent. Older adults and those with weakened immune systems face the highest risk.

West Nile virus typically peaks in late summer and early fall but has been reported in every contiguous U.S. state since its detection in New York in 1999. While human cases are often underreported, especially mild ones, mosquito activity remains active across many regions. Health officials urge precautions to protect against the virus as mosquito season persists.