A child contracted the plague while camping at Yosemite National Park in mid-July, and health officials are investigating how the child possibly caught the disease.
The California Department of Public Health said that the child went to the Stanislaus National Forest and camped at Crane Flat Campground in Yosemite National Park before coming down with the plague. Other people from the camping group have not shown any symptoms, the state health department said in a press release Thursday.
The child is now recovering, but health officials are still monitoring the child's condition, as well as the health of the family members and medical treatment providers.
"Human cases of plague are rare, with the last reported human infection in California occurring in 2006," said Dr. Karen Smith, director of the California Department of Public Health and state health officer, according to the press release.
Smith reminded everyone to avoid contact with wild rodents like squirrels and chipmunks that may be roaming around camping areas. She added that people should especially avoid touching dead rodents.
"Protect your pets from fleas and keep them away from wild animals," Smith said.
The plague is caused by the bacterium Yersinia pestis. Humans usually contract the disease when they are bitten by a rodent flea that is carrying the bacterium, and sometimes humans come down with the plague after touching an infected animal. The plague is known for causing the death of millions of people across Europe in the Middle Ages, according to the Center for Disease Control and Prevention.
The illness can be treated by antibiotics. However, without immediate medical attention, the plague can cause complications and even death. Only 1,006 cases of human plague have been recorded in the U.S. from 1900 to 2012, and 80 percent of these were in the bubonic form. Half of human plague cases occur in people aged 12 to 45, the CDC noted.
State health officials, park officials, the Los Angeles County Department of Health and the CDC are all working together to identify where the child caught the plague. They are tracking the child's activities to determine the possible point of contact with the disease, The Los Angeles Times reported.
The case follows the recent death of two Colorado residents who came down with the plague after being exposed to infected fleas. The first death occurred in June, while the second death happened early this month.
