A man was diagnosed with bubonic plague in El Dorado County, California, on August 21, 2025, after being bitten by a flea while camping. The infection, caused by the Yersinia pestis bacterium, is rare but potentially deadly, and U.S. health authorities are closely monitoring the case. The patient, whose identity remains undisclosed, is recovering at home under medical care. This case highlights the ongoing presence of the bacterium in rural western U.S. areas, where wild rodents are primary hosts. Authorities emphasize preventive measures, such as using repellents and controlling fleas on pets, to avoid further infections.
The plague, historically known as the Black Death, is a severe infectious disease that manifests in three forms: bubonic, pneumonic, and septicemic. Though rare today, with an average of seven cases annually in the U.S., its transmission through fleas or contact with infected animals requires constant vigilance. The last reported case in El Dorado was in 2020, making this new diagnosis a significant public health event.
- Forms of plague: Bubonic (swollen lymph nodes), pneumonic (spread via respiratory droplets), and septicemic (bloodstream infection).
- Prevention: Use repellents, clear rodent habitats, and treat pets for fleas.
- Treatment: Antibiotics administered early can be lifesaving.
Risks in rural areas
The plague is more prevalent in rural western U.S. regions, where wild rodents like squirrels and rats carry fleas infected with Yersinia pestis. According to the Centers for Disease Control and Prevention (CDC), California is among the states with higher incidence due to the bacterium’s presence in natural ecosystems. The recent El Dorado case underscores the need for heightened caution during outdoor activities like camping and hiking.
Local authorities have been monitoring high-risk areas, particularly in mountainous and forested regions. The 2020 case in the same area reinforces the importance of preventive measures. The CDC advises campers to avoid direct contact with rodents and wear protective clothing in endemic areas.
- High-risk areas: Western U.S., including California, New Mexico, and Arizona.
- Incidence: Average of seven human cases per year in the U.S.
- Hosts: Wild rodents such as squirrels, rats, and rabbits.
- Transmission: Flea bites or contact with infected animal fluids.
Symptoms and severity of plague
Symptoms of plague typically appear within two weeks of exposure to the bacterium. The bubonic form, the most common, causes high fever, chills, weakness, and painful swelling of lymph nodes, known as buboes. The pneumonic form, rarer, affects the lungs and can spread through respiratory droplets, while the septicemic form is the most severe, potentially fatal if untreated.
Treatment with antibiotics like doxycycline or gentamicin is highly effective when started early. In the El Dorado case, prompt diagnosis enabled successful intervention, and the patient is recovering. However, delayed treatment can increase mortality rates, particularly for septicemic plague, which can reach up to 90% without medical care.
- Main symptoms: Fever, chills, weakness, buboes, breathing difficulties (in pneumonic form).
- Incubation period: 2 to 14 days after exposure.
- Treatment: Antibiotics within 24 hours of symptom onset.
- Mortality rate: Up to 90% untreated; less than 15% with early intervention.
Strengthened preventive measures
To prevent further cases, the CDC and El Dorado authorities have intensified awareness campaigns. Clearing areas near homes, such as removing brush and debris that attract rodents, is a key recommendation. Using DEET-based repellents and treating pets with flea-control products are practical and effective measures.
Campers are urged to avoid areas with high rodent populations and never feed wild animals. Long-sleeved clothing and long pants also reduce the risk of flea bites. Warning signs are often placed in trails and campsites in endemic areas to alert visitors to potential risks.
- Camping precautions: Use repellents, avoid rodents, and protect food.
- Pet protection: Regularly apply flea-control products.
- Environmental hygiene: Clear woodpiles, trash, and brush near homes.
- Protective clothing: Long sleeves and pants in high-risk areas.
Historical context of the plague
The plague is one of history’s most feared diseases, responsible for devastating pandemics like the Black Death in the 14th century, which killed millions in Europe. Though rare today due to medical advances, it remains active in parts of Africa, Asia, and the Americas. In the U.S., cases are concentrated in the west, but sporadic outbreaks have occurred in countries like Madagascar and China.
Recent studies found Yersinia pestis in DNA from 3,300-year-old Egyptian mummies, showing the bacterium has infected humans for millennia. Advances in diagnostics and treatment have transformed the plague from a death sentence to a treatable condition, provided it is caught early.
- Historical pandemics: Black Death (14th century), Justinian Plague (6th century).
- Global occurrence: Recent cases in Madagascar, China, and Mongolia.
- Medical advances: Antibiotics and rapid diagnostics have reduced lethality.
- Curiosity: Medieval doctors wore beak-like masks to avoid infection.
Surveillance and authorities’ response
U.S. health authorities maintain an active surveillance system to monitor plague cases. In El Dorado, teams are inspecting camping areas to identify potential rodent hotspots. Regular testing of wild animals helps map the bacterium’s presence. Educational campaigns are also being ramped up to inform the public about risks and prevention.
The current case does not indicate an outbreak risk, but it serves as a reminder of the need for prevention. The CDC notes that bubonic plague is not easily transmissible between humans, but pneumonic plague requires immediate isolation to prevent spread. No additional cases linked to the El Dorado patient have been reported.
- Monitoring: Inspections in rural areas and rodent testing.
- Educational campaigns: Flyers and signs at campsites.
- Isolation: Required only for pneumonic plague cases.
- Rapid response: Early diagnosis prevents severe complications.
