First West Nile Virus of 2024 confirmed in mosquitos in eastern Montana

Culex species mosquitoes spread West Nile virus. (Photo courtesy U.S. Centers for Disease Control and Prevention)

Local and state officials on Monday reported the first cases of West Nile Virus of 2024 have been found in mosquitos in four counties in eastern Montana.

The Department of Public Health and Human Services reported that the virus was detected in mosquitos from six different pools in Blaine, Dawson, Prairie and Wibaux counties. Typically, the first detection in mosquitos means the virus will be found in humans or horses within about two weeks.

“Now is the time to take action against West Nile Virus if you haven’t already started thinking about mosquito bite prevention this season,” said DPHHS Vectorborne Disease Epidemiologist Devon Cozart. “Infection can result in minor or severe illness, including death.”

DPHHS said the virus risk will persist likely through October, when mosquitos become less active in Montana.

Many people who contract the virus show no symptoms, but about 20% can develop headaches, body aches, fatigue, vomiting and diarrhea that can last for weeks for some people. But about 1 in 150 people can develop neuroinvasive West Nile, which can lead to long-term neurological issues and in rare cases death.

There is no vaccine or medications for humans who contract the virus, but horses can be vaccinated annually to protect against the virus.

“Even minor forms of infection can leave individuals feeling ill and fatigued for weeks,” Cozart said.

People are advised not to keep standing water around their homes to prevent mosquitos from breeding there and to use insect repellant and long-sleeved shirts and pants to prevent bites. More information on the virus and prevention can be found on the DPHHS website.