West Nile virus activity reported in California and Maryland

Health officials in California and Maryland are issuing warnings regarding the presence of West Nile virus. In Calaveras County, California, two sentinel chickens in the Copperopolis area tested positive for the virus on September 25, 2026. While no human cases have been reported in Calaveras County this year, the positive results indicate that mosquitoes carrying the virus are active in the region. This follows a human infection reported in neighboring Tuolumne County in late August.

In Maryland, the Department of Health reported the state’s first confirmed human case of 2026 in July. Health officials emphasize that the virus is present across various jurisdictions in the state. To mitigate risks, authorities recommend using EPA-registered insect repellents, wearing long sleeves and pants, and eliminating standing water in containers, gutters, and birdbaths to prevent mosquito breeding.