Health officials suspect an infected flea was responsible for spreading plague to a South Lake Tahoe resident, authorities announced on Aug. 19.

The victim tested positive for plague—the same disease responsible for the black death that killed 25 million Europeans in the Middle Ages.

Plague is now treatable with antibiotics if detected early.

The resident was camping in the South Lake Tahoe area and possibly bitten by the infected flea, according to El Dorado County, and is now recovering at home under the care of a medical professional.

Health officials are investigating the situation.

“Plague is naturally present in many parts of California, including higher elevation areas of El Dorado County,” said Kyle Fliflet, El Dorado County’s acting director of public health. “It’s important that individuals take precautions for themselves and their pets when outdoors, especially while walking, hiking, and or camping in areas where wild rodents are present.”

Plague is caused by the Yersinia pestis bacterium. The bacteria are most often transmitted by the bites of fleas that have acquired the bacteria from infected squirrels, chipmunks, and other wild rodents, according to county officials.

Dogs and cats can also bring infected fleas into a home, where people can be bitten by them.

Plague can be prevented by avoiding contact with wild rodents and by keeping pets away from rodent burrows.

Infected people can show symptoms within two weeks of exposure to an infected animal or flea. The symptoms include fever, nausea, weakness, and swollen lymph nodes, health officials said.

About seven human plague cases are reported each year in the United States, according to the Centers for Disease Control and Prevention.

A souvenir shop in South Lake Tahoe in July 2024. Health officials warned the public on Aug. 19, 2025, to take precautions outdoors in the area after a resident was diagnosed with plague. (Jill McLaughlin/The Epoch Times)

The last plague epidemic in the U.S. occurred in Los Angeles from 1924 to 1925, when 30 people died.

Since then, plague has spread from urban rats to rural rodent species and has become entrenched in many areas of the western United States, the CDC reported. Most human cases are found in northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and far western Nevada.

California health department officials closely monitor for plague in the state. Surveillance in El Dorado County from 2021 to 2024 found a total of 41 ground squirrels or chipmunks exposed to the plague bacterium. This year, four more rodents have tested positive. All of the animals were found in the Tahoe Basin, according to county health officials.

Human cases are rare. Before the current case, the most recently reported case of human plague in El Dorado County was in 2020.

Two people were reported to have the disease in 2015 after having been exposed to infected rodents or fleas in Yosemite National Park.

All of those infected were treated and recovered, according to El Dorado County. They were the first reported human cases in California since 2006.