West Nile virus cases reported across multiple U.S. states

Multiple regions across the United States are reporting West Nile virus activity in both humans and animals during the 2026 season.

In Illinois, the first human case has been confirmed in Piatt County, with three additional probable cases in northern Illinois. Similarly, Massachusetts has recorded three human cases, including one in Boston. In Indiana, the first case of the year was reported in Allen County, while New York has seen four cases, including one in Nassau County. Colorado also reported three new cases in Montrose County.

Animal infections are also rising. In Utah, five horses in Cache and Weber counties tested positive. Minnesota reported its first case of the year in a horse in Polk County, following positive mosquito tests in three counties.

Health officials emphasize that while many infections are asymptomatic, the virus can cause severe neurological complications, particularly in older adults and those with weakened immune systems. Public health departments are urging residents to use insect repellent, wear protective clothing, and eliminate standing water to reduce mosquito breeding sites.