deer mouse

Hantavirus is a rare but deadly virus that is spread by infected rodents. It is an airborne disease that does not spread from person to person. The infection is spread by inhaling particles from rodent droppings. The disease does not affect the mice themselves but can make people seriously ill. About 30-40% of people who contract the virus die from it.

In San Diego County, deer mice are the main carriers of hantavirus. They are mostly found in rural areas, the desert, and mountains. Mice that commonly live with humans are house mice and do not carry hantavirus. However, you should avoid contact with all wild rodents because they may carry other diseases.

Excluding rodents from homes, cabins, sheds, and other structures, airing out unused structures before entering, and using a wet cleaning method and other safe cleaning practices (described below) can reduce your exposure to hantavirus. 

The Vector Control Program routinely collects blood samples from wild mice to test for hantavirus. If positive results are found, the public is notified of appropriate precautions to take to lower risk of exposure.

Hantavirus Detections in San Diego County



Symptoms may appear 1 to 8 weeks after exposure to rodents or their droppings. Initial symptoms include:

  • Severe muscle aches
  • Chills and fever
  • Headache or dizziness
  • Difficulty breathing or coughing
  • Respiratory problems/failure
  • Nausea, vomiting, or stomach pain

Contact your doctor immediately if you experience these symptoms. There is no treatment or vaccine for hantavirus infection, but medical care can help reduce the symptoms during recovery. 

Rodent Exclusion

Keep rodents from entering homes, cabins, sheds, and other structures:

  • Seal all entry holes large enough for mice (dime-size or larger)
  • Cover or put away pet food dishes when not in use
  • Store pet food in rodent-proof containers
  • Cover all trash cans with rodent-proof lids
  • Use mouse traps where there is evidence of mouse activity
  • Remove woodpiles, old cars, trash, and debris from property
  • Store hay or firewood at least 100 feet away from buildings
  • Cut grass, weeds, and trim bushes within 100 feet of buildings

Safe Cleaning Practices

Lower your exposure to airborne particles when cleaning up rodent droppings:

  • Air out unused rooms or buildings that have been empty for a long period of time. Leave doors and windows open for 30 minutes
  • Wear latex or rubber gloves and protective respiratory equipment, such as a face mask
  • DO NOT stir up dust by sweeping up or vacuuming rodent droppings, urine, or nesting materials
  • Instead, use the WET CLEANING method:
    1. Make a disinfectant solution (10 parts water to 1 part bleach) or use a commercial disinfectant making sure to follow the label instructions
    2. Spray the disinfectant solution on polluted areas, including dead rodents or droppings, and let sit for 15-20 minutes before cleaning
    3. Soak sponges in the disinfectant solution and clean
    4. Place dead rodents, nesting material, and all cleaning supplies in a sealed plastic bag and throw bag away immediately
    5. After cleaning, wash your gloved hands, remove the gloves and dispose of them, and then wash your bare hands as well


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Deer Mouse photo by Seney Natural History Association
Hantavirus photo by CDC/ Cynthia Goldsmith, Luanne Elliott