More Wild Mice Test Positive for Hantavirus


County Vector Control officials are reminding people to avoid rodents in the wild and to never sweep up or vacuum up rodent infestations if they find them in their homes, sheds and garages after more wild mice have tested positive for hantavirus.

Vector Control officials said five Western harvest mice caught in routine trapping in open fields in 4S Ranch and in the rural Black Mountain area have tested positive for hantavirus, bringing this year’s total number of rodents to test positive to 17. That is the highest number of rodents to test positive in San Diego County since 2012, when 35 mice and one meadow vole tested positive over the course of the year.

Vector Control officials said the high number was not a cause for alarm. Hantavirus is common in San Diego County, but it is mainly carried by wild mice that do not live around humans so people are rarely exposed to the virus. In addition, the 17 rodents that tested positive represent 4.8 percent of the 351 wild rodents that Vector Control has trapped  and tested this year, a figure within normally-expected ranges.

Still, officials said people should remember to protect themselves from potentially being exposed to hantavirus. The virus can cause deadly infections in people and there is no vaccine or cure for it.

Infected rodents shed hantavirus through their saliva, urine and feces. When that matter dries, it — and the virus — can be stirred into the air if swept or vacuumed, where it can then be breathed in by people.

The 17 rodents that have tested positive for hantavirus this year were trapped in open fields and rural areas away from homes and people in Borrego Springs, Boulevard, Julian, Ramona and San Diego and Santa Ysabel.

Vector Control officials said people stand very little chance of being exposed to the virus if they keep wild rodents out of their homes and workplaces.

Avoid Exposure to Hantavirus:

  • Seal up all external holes in homes, garages and sheds larger than a dime 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 droppings and urine.
  • Clean up rodent droppings and urine using the wet cleaning method described below.

Use “Wet-cleaning” Methods to Prevent Inhaling the Virus:

  • Do not sweep or vacuum infested areas.
  • Ventilate affected area by opening doors and windows for at least 30 minutes.
  • Use rubber gloves. Spray a 10 percent bleach solution or other disinfectants onto dead rodents, rodent droppings, nests, contaminated traps, and surrounding areas and let the disinfectant stand for at least 15 minutes before cleaning.
  • Clean with a sponge or a mop.
  • Place disinfected rodents and debris into a plastic bag, seal the bag and place it into a second plastic bag. Seal the second outer bag and discard both bags into a covered trash can.
  • Wash gloves in a bleach solution, then soap and water, and 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 (DEH) at (858) 694-2888 or visit the DEH hantavirus web page.


Gig Conaughton is a communications specialist with the County of San Diego Communications Office. Contact