2 people in Wyoming found with West Nile virus

CASPER (WNE) — Two human cases of West Nile virus have been confirmed in Wyoming so far this year. Last year, there were only two cases in the whole year, and the state has yet to face the most attractive month for mosquitos. 

Historically, August has had the highest number of West Nile cases over the last 10 years, according to data compiled by the Wyoming Department of Health. 

July and September are the next two most popular months for cases to be diagnosed. 

Although Wyoming has caught up with 2024, it is still not near the number of cases seen in 2023, when the state saw an abnormal number of cases, totaling 27 with four deaths. 

Excluding 2023, Wyoming has stayed on track with the United States’ infection rate for the last 10 years. In 2023, more than 16% of the mosquito pools tested were positive for the virus. 

Of the pools tested this year, 10% have come back positive. 

Of the two cases found this year, one is a case of the neuroinvasive disease and it was found in Natrona County. Natrona County also has one confirmed presumptive viremic donor. 

According to the Centers for Disease Control and Prevention, presumptive viremic donors are “people who had no symptoms at the time of donating blood through a blood collection agency, but whose blood tested positive when screened for the presence of West Nile virus.” 

The CDC also says that these donors may later develop symptoms. It remains unclear whether the cases in Natrona are the same person or two different people. The other case is categorized as a human fever case, and it was found in Goshen County. 

This story was published on July 31, 2025.