On August 20, 2025, health officials in El Dorado County, California, confirmed a new human case of plague in a resident of South Lake Tahoe. The patient, whose identity has not been disclosed, is currently recovering at home under medical supervision. According to the El Dorado County Environmental Management Division and Public Health Division, the individual likely contracted the infection after being bitten by a flea while camping in the scenic South Lake Tahoe area—a popular destination for outdoor enthusiasts drawn to its forests and mountain vistas.
This latest case has prompted renewed attention on an ancient but still-present threat: the plague, caused by the bacterium Yersinia pestis. While the word "plague" might conjure images of medieval pandemics, the disease remains naturally present in many parts of California, especially in higher elevation regions like El Dorado County. "Plague is naturally present in many parts of California, including higher elevation areas of El Dorado County," said Kyle Fliflet, the county’s acting director of public health, in a statement reported by KTXL. "It’s important that individuals take precautions for themselves and their pets when outdoors, especially while walking, hiking, or camping in areas where wild rodents are present."
The county’s public health team is actively investigating the circumstances surrounding the infection, but they believe the patient’s illness stems from a flea bite during a recent camping trip. Fleas that have fed on infected rodents—like squirrels and chipmunks—are the primary vectors for transmitting Yersinia pestis to humans. Pets, particularly cats and dogs, can also carry plague-infected fleas into homes, increasing the risk to humans.
Plague infections in humans are rare in California, but they are not unheard of. According to the Centers for Infectious Disease Research and Policy, the last reported human case in El Dorado County occurred in 2020, under similar circumstances. Prior to that, two people were infected in 2015 after visiting Yosemite National Park. Both of those earlier patients recovered following prompt medical treatment. Statewide, these sporadic cases were the first in California since 2006.
Surveillance efforts by the California Department of Public Health and El Dorado County have been ongoing. From 2021 through 2024, officials identified 41 rodents in the county that had been exposed to the plague bacterium. In 2025 alone, four additional rodents tested positive in the Tahoe Basin, underscoring the persistent presence of the disease in local wildlife populations.
There are three main types of plague: bubonic, septicemic, and pneumonic. Bubonic plague is the most common form and is typically caused by flea bites. Its symptoms—fever, nausea, weakness, and swollen lymph nodes—usually appear within two weeks of exposure. If left untreated, bubonic plague can progress to septicemic plague, which shares similar symptoms and can develop from handling infected animals. The most serious form, pneumonic plague, can arise if the bacteria reach the lungs. According to the CDC, pneumonic plague’s incubation period can be as short as a single day, and it is the only form of plague that can be transmitted from person to person through respiratory droplets. Fortunately, El Dorado County officials have not specified which type of plague the current patient contracted, but they emphasize that all forms require swift medical attention.
Timely antibiotic treatment is crucial. “With quick treatment, about 90% of those infected survive,” the Cleveland Clinic noted in a statement cited by KTXL. However, without medical intervention, “plague is nearly always fatal.” This stark reality underscores the importance of both public awareness and rapid response by health authorities.
To prevent plague, health officials offer several practical tips. People should avoid contact with wild rodents and refrain from feeding squirrels, chipmunks, or similar animals. Pets should be kept away from rodent burrows, and flea control products are strongly recommended for animals that spend time outdoors. When camping or hiking, wearing long pants and applying insect repellent containing DEET—especially on socks or pant cuffs—can help reduce the risk of flea bites. If a sick, injured, or dead rodent is encountered, it should not be touched, and pets should be prevented from interacting with such animals.
For pet owners, the risks are real. Cats are especially susceptible to the plague and can become seriously ill after interacting with infected rodents, potentially passing the disease to humans. If a pet becomes sick after being outdoors in a known plague area, veterinary care should be sought immediately.
Anyone who develops symptoms—such as fever, nausea, weakness, or swollen lymph nodes—within two weeks of visiting an area known for plague activity should consult a physician without delay. Early diagnosis and antibiotic treatment are highly effective and can mean the difference between full recovery and severe illness.
While the South Lake Tahoe case is the first reported in El Dorado County since 2020, other parts of the western United States have also seen sporadic plague activity in recent years. Earlier this year, northern Arizona recorded its first pneumonic plague-related death since 2007, though health officials have not disclosed how the patient became infected. In Oregon, a 2024 case of bubonic plague was believed to be linked to a pet cat—the first such case in that state since 2015. Colorado has reported instances of both septicemic and bubonic plague in animals, including cats, prairie dog colonies, and squirrels.
Despite its fearsome reputation, plague is not highly contagious in its most common forms, and human cases remain exceedingly rare. Still, as El Dorado County’s case demonstrates, the bacterium persists in rodent populations, and the risk—however small—remains present for those who venture into affected areas. Public health officials continue to monitor rodent populations and urge residents and visitors alike to heed posted warnings and take sensible precautions.
For those planning to enjoy the outdoors in California’s high country, the message from health officials is clear: be vigilant, protect yourself and your pets, and don’t ignore warning signs—both literal and physical. The ancient scourge of plague may never disappear entirely, but with awareness and quick action, its threat can be kept firmly in check.
