Placer County Reports First Human West Nile Virus Case

Placer County has recorded its first human West Nile virus (WNV) case this season, coinciding with heightened mosquito activity and a significant statewide increase in infections. As of September 24, 2026, statewide WNV cases are more than three times higher than at this point last year. The individual in Placer County may have contracted the virus elsewhere, with no details shared on their symptoms or exact location. Officials stress that the risk for WNV transmission remains high locally, with additional cases expected as fall progresses.

Since June, nine dead birds and 112 mosquito samples in Placer County have tested positive for the virus. Dr. Rob Oldham, the county's health officer, urged residents to implement preventative measures, highlighting that while most WNV infections are mild, severe illness, hospitalization, and fatalities can occur. The Placer Mosquito and Vector Control District continues its weekly surveillance and mosquito control efforts. Other nearby counties, including Yolo, Butte, and Stanislaus, have also reported WNV cases and deaths this season, underscoring the widespread nature of the threat.