As campgrounds and summer cabins reopen in California's mountains and foothills, visitors should remember that these beautifully remote areas are home to the bubonic plague and the hantavirus, cautions Dr. Bruno Chomel, an epidemiologist at the UC Davis School of Veterinary Medicine. "Although the incidence of hantavirus and the plague are highest when rodent populations peak during summer and fall, these diseases are spread year-round," says Chomel, who is helping government officials track both diseases. Hantavirus, which causes a flu-like illness that attacks the lungs, is transmitted in deer mouse droppings. Anyone cleaning out a mountain cabin that has mouse droppings should wear a mask and bleach the floor before sweeping or vacuuming, Chomel recommends. Bubonic plague, appearing in humans as a fever with inflammation and swelling of the lymph nodes, is carried by fleas from ground squirrels. One fatal case of the plague was reported last month in Kern County. Campers should put flea spray and collars on pet cats or dogs that accompany them, suggests Chomel. "In all cases, people should not touch sick or dead animals, but should, instead, report them to a ranger," he says.