Health officials in California say they are looking into a second suspected case of plague, in a tourist who recently visited the state's Yosemite National Park.
The announcement comes less than two weeks after a confirmed diagnosis of plague in a child who had camped at a park campground.
Tests are being conducted on a person from Georgia who toured Yosemite, the Sierra National Forest and other surrounding areas, officials at the California Department of Public Health said.
After the confirmation of plague in the child visiting from Los Angeles County with family, health officials had closed two campgrounds, notifying park visitors.
The child has recovered, and no other members of the family have reported any symptoms, authorities say.
Park officials confirmed the presence of plague in squirrels at Crane Flat and Tuolumne Meadows campgrounds in the park and closed them.
An infectious bacterial disease, plague can be carried by squirrels, chipmunks and other wild rodents. When an infected rodent becomes sick and dies, fleas it has been carrying can transfer the infection when biting other warm-blooded animals, including humans.
The risk of a human contracting plague remains low, according to health officials, who have been working with the National Forest Service and the U.S. Centers for Disease Control and Prevention to test places where the Georgia tourist visited.
"The California Department of Public Health and Yosemite National Park were very proactive in their campaign to educate visitors about plague," state Health Director Dr. Karen Smith said.
"Warnings issued in California regarding plague were useful all the way across the country in Georgia. Those warnings helped the patient get the prompt medical attention necessary to recover from this illness."
Symptoms of the disease, which can be fatal if untreated, can include high fever, nausea, chills or weakness. It also can cause lymph nodes to swell in armpit, neck or groin.
The last reported case of human plague in California was in 2006; the state has confirmed 42 cases of plague in humans since 1970, with 9 people dying from the disease.
The two recent California cases follow announcements out of Colorado of two fatal cases of plague there this year – in a teenager and an adult – likely contracted "from fleas on a dead rodent or animal."