State health officials are investigating a case of human plague after a child from Los Angeles became ill and was hospitalized after visiting Stanislaus National Forest and camping at Crane Flat Campground in Yosemite National Park in mid-July.
No other members of the camping party reported symptoms, and health officials said Thursday that the child is recovering.
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 or humans.
Plague is infamous for killing millions of people in Europe during the Middle Ages.
“Human cases of plague are rare, with the last reported human infection in California occurring in 2006,” said Dr. Karen Smith, the state’s health officer.“Although this is a rare disease, people should protect themselves from infection by avoiding any contact with wild rodents. Never feed squirrels, chipmunks, or other rodents in picnic or campground areas, and never touch sick or dead rodents. Protect your pets from fleas and keep them away from wild animals,” she said.
The California Department of Public Health is working closely with the Los Angeles County Department of Public Health, U.S. Centers for Disease Control and Prevention, Yosemite National Park and the U. S. Forest Service to investigate the source of the infection, and the patient’s travel history and activities during the incubation period.
The case of plague comes three years after a hantavirus outbreak at Yosemite in 2012. Ten tourists fell ill to hantavirus carried by deer mice. In nine of the cases, investigators determined that deer mice had nested inside the double walls of tent-cabins in Yosemite’s Curry Village. After the outbreak, old tents were torn down and workers made changes to tents to prevent mice from burrowing inside.
On Thursday, after the identification of the human case of plague, health officials said Yosemite National Park will provide additional information to visitors about steps to prevent plague exposure, and post caution signs at the Crane Flat campground and nearby campgrounds. 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, hiking 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 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. Plague is treatable in its early stages with prompt diagnosis and proper antibiotic treatment. If not treated, plague can be fatal.
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. Since 1970, 42 human cases of plague have been confirmed in California, of which nine were fatal.
Plague is not transmitted from human to human, unless a patient with plague also has a lung infection and is coughing. There have been no known cases of human-to-human infection in California since 1924.