A man was hospitalized in El Dorado County, California, after being diagnosed with bubonic plague, a rare infection caused by the Yersinia pestis bacteria, transmitted through a flea bite during a camping trip, as announced by health authorities on August 21, 2025. The patient, whose identity was not disclosed, is recovering at home under medical supervision with antibiotic treatment. This is the first case reported in the region since 2020, prompting authorities to heighten prevention alerts in rural and camping areas. The plague, historically linked to devastating pandemics, remains present in wild rodents in the western United States, requiring vigilance from campers and residents. The case underscores the need for preventive measures against fleas and rodents to avoid further infections.
The incident occurred in a mountainous area known for its population of wild rodents, such as squirrels, which are natural reservoirs for the bacteria. The U.S. Centers for Disease Control and Prevention (CDC) reports an average of seven human plague cases annually in the country, with most occurring in states like California, New Mexico, and Colorado.
- Preventive measures include using DEET-based repellents.
- Avoiding contact with wild rodents is essential to reduce risks.
- Pets should be regularly treated for fleas.
The current situation shows no signs of an outbreak, but it highlights the importance of vigilance in natural areas.
Origin of the bacteria and risks in rural areas
Bubonic plague is caused by Yersinia pestis, a zoonotic bacterium that circulates among rodents and fleas in natural environments. In El Dorado County, the presence of squirrels and marmots facilitates the bacteria’s persistence in the ecosystem. The recent case, reported in a camping area, reignites concerns about human exposure in rural regions.
Transmission occurs primarily through bites from infected fleas, which contract the bacteria after feeding on sick animals. Direct contact with bodily fluids from infected rodents also poses a risk. The El Dorado patient, who developed symptoms after outdoor activity, was diagnosed quickly, allowing for immediate treatment.
Local authorities, in collaboration with the CDC, are monitoring the bacteria’s circulation in wild rodents. In 2020, a similar case in the same region prompted educational campaigns, which are now being reinforced. The swift medical response in the current case demonstrates the effectiveness of antibiotics, such as doxycycline, when administered early.
Forms of the disease and warning signs
The plague manifests in three main forms, each with distinct symptoms and risks:
- Bubonic: Characterized by painful swelling of lymph nodes (buboes), it is the most common and least severe form if treated early.
- Pneumonic: Affects the lungs and can be transmitted through respiratory droplets, increasing the risk of contagion.
- Septicemic: The bacteria spread through the bloodstream, potentially leading to severe complications like septic shock.
- Early diagnosis: Symptoms such as fever, chills, and localized pain require immediate attention, especially after exposure to high-risk areas.
In the El Dorado case, the patient presented the bubonic form, with symptoms like high fever and swollen lymph nodes, successfully treated. The pneumonic form, though rare, is more concerning due to its potential for human-to-human transmission. The septicemic form, less common, can progress rapidly if untreated.
Early diagnosis is critical. Individuals frequenting rural or camping areas should watch for symptoms appearing within two weeks of potential exposure and seek medical care immediately.
Preventive measures for campers and residents
Preventing the plague relies on practical steps to minimize contact with fleas and rodents. Health authorities recommend:
- Using DEET-based repellents on exposed skin during outdoor activities.
- Avoiding camping near rodent colonies or piles of debris that may attract animals.
- Treating pets with flea control products to prevent the introduction of infected fleas into homes.
- Keeping yards and residential areas free of trash or dense vegetation that may harbor rodents.
Local campaigns in El Dorado are distributing educational materials in parks and camping areas, providing guidance on identifying dead rodents, which may indicate the presence of the bacteria. The CDC also advises that anyone experiencing fever or swollen lymph nodes after outdoor activities should seek medical attention promptly.
Public education is a key tool in endemic areas. Clearing land and reporting dead rodents help map high-risk areas, enabling swift interventions.
History of the plague in the United States
Bubonic plague arrived in North America in the early 20th century, likely through ships carrying infected rats. Since then, the bacteria have established themselves in wild rodent populations, such as squirrels, marmots, and field rats, particularly in the western U.S.
Between 1970 and 2020, approximately 500 human cases were recorded in the U.S., with an 11% mortality rate in untreated cases. States like New Mexico, Arizona, and Colorado account for the majority of cases, followed by California. The low incidence is due to ongoing surveillance and access to effective treatments.
The El Dorado case serves as a reminder of Yersinia pestis’ continued presence in nature. While medical advances have significantly reduced risks, exposure in rural areas requires constant care.
Actions by authorities to mitigate risks
El Dorado County authorities, in collaboration with the CDC, are inspecting camping areas and trails to identify potential rodent hotspots. Traps for rodents and flea testing are being used to monitor bacterial circulation.
- Active monitoring: Public health teams are conducting inspections in natural areas.
- Educational campaigns: Flyers and signs provide campers with prevention guidance.
- Rapid intervention: Suspected cases are treated immediately to prevent complications.
- National collaboration: The CDC supports local efforts with resources and guidelines.
The response to the current case was effective, with the patient recovering and no signs of transmission. However, authorities emphasize that ongoing vigilance is essential in regions where the bacteria is endemic.
Curiosities about the plague’s history
The plague has a storied past, with significant impacts on human history. Some notable points:
- In the 14th century, the Black Death killed about 50% of Europe’s population.
- Doctors wore long-beaked masks, believing they protected against the disease.
- Traces of Yersinia pestis have been found in 3,300-year-old archaeological remains.
- In the U.S., rodents like marmots are the primary bacterial reservoirs.
Though treatable today, the plague’s history underscores the importance of preventive measures and vigilance. Combining education, monitoring, and effective treatment keeps risks under control, but the bacteria’s presence in nature demands constant attention.