Deer mouse tests positive for Hantavirus in Rancho Cuyamaca State Park

By Gig Conaughton, County of San Diego Communications Office

October 29, 2025 (Cuyamaca) -- A deer mouse collected in routine monitoring Oct. 22 at the Los Vaqueros Group Horse Campground in Cuyamaca Rancho State Park has tested positive for the potentially deadly hantavirus.

Finding hantavirus in wild rodents is not uncommon in San Diego County. And people rarely come into direct contact with infected animals because wild rodents naturally avoid humans.

Even so, County officials are advising people to take precautions, especially when pulling out those holiday decorations from sheds, garages or attics in case there have been infected rodents living in those areas.

While exposure to the potentially deadly hantavirus is rare, people should be careful around wild rodents and places where they nest as there is no cure or vaccine for hantavirus.

Symptoms of hantavirus usually develop between one to eight weeks after exposure and include:

• Severe muscle aches.
• Chills, fever or fatigue.
• Headache or dizziness.
• Nausea, vomiting or stomach pain.
• Difficulty breathing.

If you think that you may have been exposed to hantavirus, seek medical attention immediately.

Preventing Infection

People can be exposed to hantavirus when wild rodents invade their living or storage areas. Infected rodents shed the virus in their urine, feces and saliva. Once the matter dries, it can be stirred into the air where people could inhale the virus.

If people find wild rodents, nests, or  their droppings in their living or storage spaces, they should always use “wet cleaning” methods — using bleach or other disinfectants, rubber gloves and bags. DO NOT SWEEP or VACUUM, which can stir hantavirus into the air where it could be inhaled. If you have to clean, use “wet cleaning” methods instead.

 Avoid Exposure to Hantavirus

• Seal up all external holes larger than a dime in homes, garages and sheds to keep rodents from getting in.
• Eliminate rodent infestations immediately.
• Avoid rodent-infested areas and do not stir up dust or materials that may be contaminated with rodent poop and urine.
• Clean up rodent poop and urine using the “wet cleaning” methods described below.

“Wet-cleaning” Methods

• Do not sweep or vacuum infested areas.
• Ventilate the affected area by opening doors and windows for at least 30 minutes before starting to clean.
• Use rubber gloves. Spray a 10% bleach solution or other disinfectants onto dead rodents, rodent poop, nests, contaminated traps and surrounding areas, then let the disinfectant stand for at least 15 minutes before cleaning.
• Clean with a sponge or a mop that has been soaked in disinfectant.
• Place disinfected rodents and debris into two plastic bags, seal them and discard them in the trash.
• Wash gloves in a bleach solution, then in soap and water, and then dispose of them using the same double-bag method.
• Thoroughly wash your hands with soap and water.

For more information, contact the County Department of Environmental Health and Quality (DEHQ) at (858) 694-2888 or visit the DEHQ hantavirus web page.