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A California resident tested positive for plague after camping in South Lake Tahoe in El Dorado County, adding to a growing list of positive plague cases in western states. California health officials believe the person was infected after being bitten by an infected flea. The infected individual is currently under the care of a medical professional and is recovering at home.
Plague in California
“Plague is naturally present in many parts of California, including higher elevation areas of El Dorado County, Kyle Fliflet, El Dorado County’s Acting Director of Public Health, said in a statement announcing the positive test. “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.”
According to the California Department of Public Health, “surveillance activities in El Dorado County from 2021 through 2024 found a total of 41 rodents (ground squirrels or chipmunks) with evidence of exposure to the plague bacterium. To date in 2025, four additional rodents have tested positive. All these rodents were identified in the Tahoe Basin.”
History of the plague
According to the U.S. Centers for Disease Control and Prevention (CDC), there are an average of seven cases of human plague reported every year in the United States. However, a cat in Colorado tested positive for the plague and died earlier this month, and last month, an Arizona resident who contracted the plague died from the disease. It was the first death from the plague in the United States since 2007.
Last year, a Colorado resident contracted the plague and another person in the state of Oregon contracted the bubonic plague. They were likely infected by their symptomatic pet cat, according to health officials. In September of 2023, a resident of Archuleta County in Colorado died as a result of contracting the plague.
The World Health Organization (WHO) describes bubonic plague as one of two main types of plague caused by the bacterium Yersinia pestis, a zoonotic bacteria usually found in small mammals and their fleas. The WHO website explains that it “is transmitted between animals and humans by the bite of infected fleas, direct contact with infected tissues, and inhalation of infected respiratory droplets.”
Bubonic plague is most often associated by people with “The Black Death” pandemic that decimated Europe between 1347 and 1351 that killed as many as 50 million people – about half of the population of Europe at the time. According to the CDC, the last urban plague epidemic in the United States occurred in Los Angeles in 1924 and 1925. It then spread from urban rats to rural rodent species and “became entrenched” in many areas of the western United States.
Signs and symptoms
In the case of the bubonic plague, according to the CDC, infected individuals develop fever, headache, chills, and weakness and one or more swollen, painful lymph nodes. In cases of septicemic plague, patients develop fever, chills, extreme weakness, abdominal pain, shock, and possibly bleeding into the skin and other organs. Skin and other tissues may turn black and die, especially on fingers, toes, and the nose. And with pneumonic plague, people develop fever, headache, weakness, and a rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery mucous.
The CDC notes that a plague vaccine is no longer available in the United States and that while new vaccines are in development, they are not expected to be commercially available in the immediate future. Infections can, however, be treated with antibiotics if they are detected early.