Yosemite National Park, California - California Department of Public Health (CDPH) Director and State Health Officer Dr. Karen Smith today announced that the department, working closely with Yosemite National Park, successfully reduced the risk of plague transmission at Crane Flat Campground in Yosemite. The campground, which had been closed for four nights to allow for rodent burrows to be treated for fleas, is reopening today.

The treatment controlled potentially plague-infected fleas which could spread the disease to humans and other warm-blooded hosts.

Based on new evidence of plague activity in animals, Tuolumne Meadows Campground in Yosemite will be closed from Monday-Friday next week for similar treatment. This flea treatment is commonly used to protect wildlife, pets and human health from this disease. Yosemite National Park remains open and all other campgrounds and facilities in the park remain open to visitors. 

Although the presence of plague has been confirmed at Crane Flat and Tuolumne Meadows campgrounds, the risk to human health remains low. Action to protect human and wildlife health by closing and treating campgrounds is being taken out of an abundance of caution. Campground visitors are being notified by Yosemite National Park of camp treatments, possible plague risks and provided information on how to prevent plague transmission. An investigation into a case of human plague in California, and environmental evaluation in the Stanislaus National Forest, Yosemite National Park and the surrounding areas led to these actions.

Plague is an infectious bacterial disease that is carried by squirrels, chipmunks and other wild rodents and their fleas. When an infected rodent becomes sick and dies, its fleas can carry the infection to other warm-blooded animals including humans.

“Although this is a rare disease, and the current risk to humans is low, eliminating the fleas is the best way to protect the public from the disease,” said Dr. Smith. “By eliminating the fleas, we reduce the risk of human exposure and break the cycle of plague in rodents at the sites. People can protect themselves from infection by avoiding any contact with wild rodents,” Dr. Smith added.

Steps the public can take to avoid exposure to human plague include:

• Never feed squirrels, chipmunks or other rodents and never touch sick or dead rodents.
• Avoid walking or camping near rodent burrows.
• Wear long pants tucked into socks or boot tops to reduce exposure to fleas.
• Spray insect repellent containing DEET on socks and pant cuffs to reduce exposure to fleas.
• Keep wild rodents out of homes, trailers, and outbuildings and away from pets.

Early symptoms of plague may include high fever, chills, nausea, weakness and swollen lymph nodes in the neck, armpit or groin. People who develop these symptoms should seek immediate medical attention and notify their health care provider that they have been camping or out in the wilderness and have been exposed to rodents and fleas.

In California, plague-infected animals are most likely to be found in the foothills and mountains and to a lesser extent, along the coast. State and local health officials regularly monitor plague-prone areas by testing animals and their fleas. In 2014, non-human plague activity was detected in animals in seven counties: El Dorado, Mariposa, Modoc, Plumas, San Diego, Santa Barbara, and Sierra.

The last reported cases of human plague in California occurred in 2005 and 2006 in Mono, Los Angeles and Kern counties and all three patients survived following treatment with antibiotics. Plague is not transmitted from human to human unless a patient with plague also has a lung infection and is coughing.

The CDPH website has plague information, including precautions people can take to minimize their risk.