Hantavirus in California

Yes — hantavirus pulmonary syndrome (HPS) caused by Sin Nombre virus has been documented across the contiguous United States, with the highest cumulative case counts in the western and southwestern states. The deer mouse (Peromyscus maniculatus) is the primary reservoir and is broadly distributed across California. As of May 2026, the Hantavirus Tracker risk index for California is 64/100, classified as high.

The current composite risk index for California is 64/100 (high). The score blends recent news mention density, ProMED-mail and CDC surveillance updates, source authority, and recency of the most recent reported event.

In the United States, HPS is a nationally notifiable condition. Confirmed cases are reported through state and territorial health departments to the CDC, which publishes cumulative state-level totals on its hantavirus surveillance page. California health authorities also issue advisories when case clusters are detected or when seasonal rodent population surges raise exposure risk in popular outdoor recreation areas.

Anyone with flu-like symptoms — fever, severe muscle aches, headache — combined with recent exposure to rodent droppings, urine, or nests should contact a healthcare provider immediately and explicitly mention the rodent exposure. HPS can progress from flu-like symptoms to severe respiratory failure within days, and early intensive-care admission improves survival. Common California exposure scenarios include cleaning cabins or sheds, rural agricultural work, and disturbing rodent nests during home renovation.

Seal holes ¼ inch and larger in homes and outbuildings, store food and pet food in rodent-proof containers, remove brush and woodpiles near dwellings, and trap rodents safely. When cleaning a rodent-contaminated space, ventilate for at least 30 minutes, wear gloves and an N95 respirator, spray surfaces with 1:10 bleach-water solution and let it soak five minutes before wiping up — never sweep or vacuum dry droppings, which aerosolizes the virus. Visitors to cabins, campsites, and rural properties in California should inspect and clean before staying overnight.