Hantavirus Infection in California

Early hantavirus symptoms appear 1-5 weeks after exposure and include: fatigue, fever (101-104°F), and severe muscle aches especially in the thighs, hips, back, and shoulders. About half of patients also experience headache, dizziness, chills, nausea, vomiting, diarrhea, and abdominal pain. These early symptoms last 3-5 days before progressing to the dangerous lung phase (coughing, shortness of breath, fluid in lungs).

Hantavirus is diagnosed through blood tests that detect antibodies to the virus. Symptoms alone mimic influenza in the early stage. Key warning signs that distinguish hantavirus from flu: sudden severe muscle aches (especially thighs and back), no sore throat or runny nose (rare with hantavirus), and progression to severe shortness of breath and coughing within 3-5 days of first symptoms. If you have been near rodents or rodent droppings and develop these symptoms, seek emergency care immediately.

Hantavirus cases are reported across the United States, with the highest concentration in the western states. States with the most reported cases historically include New Mexico, Colorado, Arizona, California, Washington, Montana, and Texas. Use the outbreak tracker above to see current confirmed cases by state. Cases can occur anywhere deer mice, cotton rats, rice rats, or white-footed mice are present.

Hantavirus Pulmonary Syndrome (HPS), the form found in the Americas, has a mortality rate of approximately 36-38%. It kills by causing fluid accumulation in the lungs, leading to respiratory failure within hours of symptom onset. There is no specific antiviral treatment — survival depends on early hospitalization and intensive supportive care with mechanical ventilation. This is why seeking medical attention at the first sign of respiratory symptoms is critical.

Hantavirus is transmitted primarily through inhalation of aerosolized particles from infected rodent urine, droppings, or saliva. You can also be infected through rodent bites or touching contaminated materials then touching your mouth, nose, or eyes. It is NOT spread person-to-person (with rare exceptions). The most common exposure is cleaning enclosed spaces (cabins, garages, sheds) with rodent infestations without proper protection.

Different rodent species carry different hantavirus strains. In North America: the deer mouse (Peromyscus maniculatus) is the primary carrier of Sin Nombre virus (the most deadly HPS strain) and is found throughout the US. Cotton rats carry Black Creek Canal virus in the Southeast. Rice rats carry Bayou virus in the South. White-footed mice carry New York virus in the Northeast. All can transmit hantavirus to humans.