SACRAMENTO – Health officials confirmed on Wednesday that an El Dorado County resident has tested positive for bubonic plague, marking the first human case of the disease in California in five years. The patient is currently under medical care and is expected to make a full recovery.

The California Department of Public Health (CDPH) and El Dorado County Public Health are jointly investigating the source of the infection. In a statement released Thursday, officials said the individual likely contracted the disease from a flea bite while walking their dog along the American River corridor or in the Tahoe Keys area, where routine surveillance has detected the plague-causing bacterium, Yersinia pestis, in local rodent populations.

"While this is a rare disease, it’s important for the public to know it is present in parts of California," said Dr. Aida Cruz, El Dorado County’s Public Health Officer. "With prompt diagnosis and treatment, it is curable. The risk to the general public is low, but we urge people to take sensible precautions when outdoors in affected areas."

This is the first reported human case in the state since two individuals were infected in the South Lake Tahoe region in 2020. Both of those patients also recovered.

Understanding Plague in the Modern Era

Plague is an ancient infectious disease caused by bacteria found in wild rodents and their fleas. While infamous for causing the "Black Death" pandemic in the Middle Ages, modern antibiotics are highly effective in treating the infection if it is detected early.

The U.S. Centers for Disease Control and Prevention (CDC) reports an average of seven human plague cases nationwide each year, with the majority occurring in rural and semi-rural areas in the western United States.

There are three main forms of plague:

• Bubonic: The most common form, resulting from a flea bite. Symptoms include fever, headache, chills, and painfully swollen lymph nodes, or "buboes." It is not directly transmissible from person to person.
• Septicemic: Occurs when the bacteria enter the bloodstream. It can arise from a flea bite or as a complication of untreated bubonic plague.
• Pneumonic: The most serious form, involving infection of the lungs. It is the only form that can be spread from person to person through respiratory droplets.

Officials have confirmed the current case is bubonic plague and have stated there is no evidence of person-to-person transmission.

Public Health Recommendations

Health authorities are not restricting access to recreational areas but have increased signage and are advising visitors and residents to take heightened precautions.

"Plague is endemic in many parts of the Sierra Nevada, including El Dorado County," the CDPH statement noted. "It is crucial to prevent flea bites for both yourself and your pets."

Officials recommend the following measures to reduce the risk of exposure:

• Avoid all contact with wild rodents, including squirrels, chipmunks, and mice. Do not touch sick or dead animals.
• Refrain from feeding rodents in picnic or campground areas.
• Wear long pants and use an insect repellent containing DEET on skin and clothing when outdoors.
• Keep pets on a leash and prevent them from exploring rodent burrows. Consult a veterinarian about flea control for pets.
• If a person or pet becomes sick after being in an area with known plague activity, seek medical or veterinary attention immediately and inform them of the potential exposure.

State and local health officials will continue to monitor rodent populations in the area for evidence of the bacteria.