Infected mouse found in Rancho Bernardo

San Diego County Vector Control officials are warning people county wide that they need to take precautions when removing dead rodents or cleaning up their nests, droppings or urine.

To prevent rodent-to-human virus transmission, officials advise using the “wet-cleaning methods,” which includes ventilating affected indoor areas for at least 30 minutes before spraying a 10 percent bleach solution (two tablespoons of bleach per cup of water) on the dead rodent or area to be cleaned.

After 15 minutes, use a sponge or mop and rubber gloves. Double bag all items to be disposed, including the gloves, prior to throwing in trash and wash hands well with soap and water, they said.

Chris Conlan, the county’s supervising vector ecologist, said the virus is not carried by the typical house mouse, but by other rodents found in the fringes of developments, in canyons, undeveloped areas of the county and rural settings.

“Deer mice tend to inhabit a lot of San Diego County,” Conlan said.

The mouse found in Rancho Bernardo was the 20th in the county that tested positive this year. In January, six harvest mice in Los Penasquitos Canyon Preserve were found with the disease.

Last year there were only 14 cases in the county, including one Northern Baja deer mouse trapped in Rancho Bernardo last August. In 2008, there were 11 cases.

Conlan said officials are not surprised to find more cases this year because mice populations tend to rise when there is sufficient or higher rainfall.

The virus, identified in 1993 during an outbreak in the Four Corners part of the United States (Arizona, New Mexico, Colorado and Utah), has been around for decades.

It causes hantavirus pulmonary syndrome (HPS) in humans. In about 35 percent of cases, this is fatal since antibiotics and many other treatments are typically not effective, according to Conlan.

The last human case in San Diego County was about five years ago and the person survived, he said.

Though not transmitted between humans, the virus is transmitted from mouse to human because of its airborne nature, officials said.

People affected typically have flu-like symptoms that result in severe breathing difficulties due to the lungs filling with fluid, Conlan said.

“Hantavirus can be deadly, but it is preventable,” said Jack Miller, director of San Diego County Department of Health.

For tips on avoiding the virus and properly cleaning potentially infected areas, go to www.sdcounty.ca.gov/deh/pests/hantavirus.html or call 858-694-2888.