A man was diagnosed with bubonic plague in El Dorado County, California, after being bitten by a flea while camping, U.S. health authorities reported on August 21, 2025. The infection, caused by the Yersinia pestis bacteria, is rare but potentially fatal, prompting authorities to intensify prevention alerts in rural areas. The patient, whose identity was not disclosed, is recovering at home under medical supervision. This is the first case reported in the region since 2020, according to an official county statement. The disease, historically linked to devastating pandemics, remains present in wild rodents in the western U.S., requiring heightened caution from campers and residents. The situation underscores the importance of preventive measures against fleas and rodents.
The case reignites concerns about the bacteria’s circulation in natural areas. The Centers for Disease Control and Prevention (CDC) records an average of seven human plague cases annually in the U.S. Transmission occurs mainly through contact with infected animals or flea bites.
- Preventive measures include using insect repellents.
- Clearing areas with potential rodent habitats is recommended.
- Pets should receive regular flea control treatments.
- Avoiding direct contact with wild rodents reduces infection risks.
Origin and circulation of the bacteria
The plague, caused by Yersinia pestis, is a zoonotic disease circulating among rodents and fleas in natural environments, particularly in rural areas of the western United States, such as California, New Mexico, and Colorado. El Dorado County, where the case was reported, is a mountainous region with a significant presence of wild rodents, facilitating the bacteria’s persistence in the ecosystem. CDC data indicates the bacteria is present in various parts of California, making constant surveillance essential.
Transmission to humans occurs primarily through bites from infected fleas carrying the bacteria after feeding on sick animals. Additionally, direct contact with bodily fluids of infected rodents or other animals can spread the disease. Though rare, the plague can be deadly if not treated early.
The current case shows no signs of an outbreak, but it reinforces the need for monitoring. In 2020, another case in the same region mobilized authorities, who intensified awareness campaigns. The patient’s recovery, with antibiotic treatment, demonstrates the effectiveness of early intervention.
Forms of the disease and symptoms
The plague manifests in three main forms, each with distinct characteristics:
- Bubonic: The most common, characterized by painful swelling of lymph nodes, known as buboes.
- Pneumonic: Affects the lungs, transmitted through respiratory droplets, making it more contagious.
- Septicemic: Occurs when the bacteria spreads through the bloodstream, potentially causing septic shock.
Symptoms typically appear within two weeks of exposure. High fever, chills, extreme weakness, and localized pain are initial signs. In the pneumonic form, breathing difficulties and chest pain predominate, while the septicemic form can progress to organ failure if untreated. Early diagnosis is critical, and treatment with antibiotics, such as doxycycline or ciprofloxacin, has a high success rate.
The El Dorado patient presented the bubonic form, the least severe, and is responding well to treatment. Pneumonic or septicemic cases are rarer but require immediate intervention due to the risk of complications.
Prevention in high-risk areas
Preventing the plague relies on simple but effective measures to avoid contact with fleas and rodents. Health authorities recommend specific actions for residents and visitors in rural areas:
- Use DEET-based repellents on exposed skin.
- Avoid camping near rodent colonies or piles of debris.
- Treat pets with flea control products regularly.
- Keep residential areas free of trash or dense vegetation.
Additionally, the CDC advises individuals with symptoms like fever or swollen lymph nodes to seek medical attention immediately, especially after outdoor activities. Public education on plague risks is a priority in endemic regions like California.
Local campaigns have encouraged land clearing and reporting sightings of dead rodents, which may indicate the bacteria’s presence. These actions help map high-risk areas and prevent new cases.
History of the plague in the US
The plague is not new to the United States, though its incidence is low. Since the early 20th century, human cases have been recorded sporadically, with higher concentrations in the western U.S. The Yersinia pestis bacteria was introduced to North America around 1900, likely through ships carrying infected rats. Since then, it has established itself in wild rodent populations, such as squirrels and marmots.
Between 1970 and 2020, the CDC documented about 500 human plague cases in the U.S., with a mortality rate of approximately 11% when untreated. Most cases occur in rural areas where contact with wildlife is more frequent. States like New Mexico, Arizona, and Colorado have the highest number of cases, followed by California.
The recent El Dorado case serves as a reminder that the plague, though controlled, remains a threat in specific areas. Epidemiological surveillance and access to antibiotics have significantly reduced risks, but prevention remains the primary tool against the disease.
Actions by health authorities
El Dorado County authorities are working with the CDC to monitor the situation. Public health teams are inspecting camping areas and trails in the region to identify potential rodent infestation sites. Additionally, informational flyers are being distributed in high-traffic areas, such as parks and campgrounds, with prevention guidelines.
The rapid response to the current case prevented the disease’s spread, but authorities emphasize the importance of ongoing preventive measures. Collaboration between local and national agencies is crucial to keeping the plague under control, especially in endemic regions.
The use of monitoring technologies, such as rodent traps and laboratory testing of fleas, has helped map the presence of Yersinia pestis. These efforts enable rapid interventions in high-risk areas, reducing the likelihood of new human cases.
Curiosities about the plague
The plague has a striking history and sparks curiosity due to its impact on historical pandemics. Some interesting facts about the disease:
- The Black Death in the 14th century killed about 50% of Europe’s population.
- Doctors at the time wore long-beaked masks to protect against “bad air.”
- Yersinia pestis bacteria was found in 3,300-year-old Egyptian mummies.
- Rodents like marmots and squirrels are the main reservoirs in the U.S.
Though treatable today, the plague’s history serves as a reminder of the importance of sanitary vigilance. The combination of prevention, early diagnosis, and effective treatment keeps the disease under control, but its presence in nature requires constant attention.
