Visitors to campgrounds and summer cabins in California's mountains and foothills 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, a flu-like illness that attacks the lungs, is transmitted in deer mouse excrement. 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 a dry cough, is carried by fleas from ground squirrels. Campers should apply flea spray and collars to any pet cats or dogs that accompany them, suggests Chomel. "In all cases, people should not touch any sick or dead animals, rather report them to a ranger," he says.