SAN DIEGO - A mouse trapped in Campo by the San Diego County Department of Environmental Health has tested positive for hantavirus, an illness that is not easily transmitted but can be fatal.

The disease is often found in rodents in San Diego's backcountry, but they rarely pose a threat to humans when they're in the wild, according to the DEH.

At home, people should be careful when cleaning up rodent debris and droppings.

An infection could cause Hantavirus Pulmonary Syndrome, which starts out like the flu but can escalate to severe breathing difficulties and, in 36 percent of case, causes death, according to county officials.

"The best way to protect against exposure to hantavirus is by keeping rodents out of your homes, garages and outbuildings," said DEH Director Jack Miller. "Hantavirus can become dangerous if infected rodents get indoors and people come into contact with their droppings."

Transmission to humans often comes from inhaling dust while cleaning, so the county suggests a wet cleaning method of rodent-infested areas. Details can be found at sdcounty.ca.gov/deh/pests/hantavirus.html.