Key TakeawaysA California resident has tested positive for the plague, the state's first confirmed human case in five yearsHealth officials suspect the person was infected by a flea bite while campingPlague is naturally present in some parts of California, particularly at higher elevations where wild rodents like squirrels and chipmunks carry the disease.THURSDAY, Aug. 21, 2025 (HealthDay News) — A resident of South Lake Tahoe, California, has been diagnosed with the plague, the state’s first human plague infection since 2020. The individual is recovering at home while receiving medical care, health officials in El Dorado County announced this week.The patient — who was camping in the South Lake Tahoe area, near the Nevada border — may have been bitten by an infected flea, officials said in a news release. An investigation is underway."Plague is naturally present in many parts of California, including higher elevation areas of El Dorado County," said Kyle Fliflet, the county’s acting public health director. "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.”The disease, caused by the bacterium Yersinia pestis, is most commonly transmitted to humans by fleas that have acquired it from infected wild rodents such as squirrels and chipmunks, according to the U.S. Centers for Disease Control and Prevention (CDC). People can also be infected while handling infected animals. Dogs and cats may also carry infected fleas.While the plague gained a fearsome reputation as the cause of the millions of deaths in Europe in the Middle Ages, modern treatment with common antibiotics can be highly effective if the disease is diagnosed and treated early.Symptoms typically appear within two weeks of exposure and can include fever, nausea, weakness, headache and swollen lymph nodes.The California Department of Public Health noted that while no human cases have been reported since 2020, authorities found evidence of plague exposure in 41 rodents around the South Lake Tahoe area between 2021 to 2024, according to NBC News.In addition, four rodents have tested positive so far in 2025, all in the Tahoe basin.Health officials are urging residents and visitors to be aware of the risk and to take simple precautions.Individuals should not “touch squirrels, chipmunks or other wild rodents, especially those that are dead or injured. People should not camp near where dead rodents were observed, and they should wear long pants tucked into boots and spray bug repellent to reduce flea exposure,” officials warned in a news release.The CDC also encourages people to make sure pets are protected with flea control products. People should also avoid sharing a bed with pets that roam in exposed areas and make their property less attractive to rodents by clearing brush, rock piles and other hiding spaces and by removing potential food supplies.More informationThe U.S. Centers for Disease Control and Prevention has more about how the plague spreads.SOURCES: El Dorado County, news release, Aug. 19, 2025; NBC News, Aug. 20, 2025.What This Means For YouWhen spending time outdoors in areas with wild rodents, especially in higher elevations of California, people should take precautions against plague: They should use insect repellent, wear long pants, and keep pets on a leash to prevent contact with sick animals..Sign up for our weekly HealthDay newsletter