West Nile Virus is back in Montana, with four diagnosed cases this week.

“One of the cases is what is called a viremic donor and that is somebody who probably did not have any symptoms, but the virus was found through screening related to blood donations,” said Karl Milhon, Supervisor of the Communicable Diseases Epidemiology Section of the Department of Health and Human Services. “We’ve also had three human cases in Dawson County, on the eastern side of the state. We’ve also had some equine cases.”

The viremic donor was found in Garfield County, but Milhon says mosquito pools have tested positive for West Nile Virus all over the state.

“We’ve had mosquito pools in the west, in Lake County,” Milhon said. “Everybody needs to be concerned. Right now is the prime time for transmission of West Nile Virus. Generally, during August and September, 90 percent of our cases are diagnosed in that period.”

Most years, the number of West Nile Virus cases in Montana are in the single digits, however there have been over 200 cases some years. DPHHS advises the public to get rid of standing water near homes and to wear insect repellent, especially near dawn and dusk when mosquitoes are most active.