Black Death resurfaces in the US and reignites Brazil’s focus on health surveillance
A recent death caused by the Black Death in Coconino County, Arizona, United States, confirmed on July 11, 2025, has raised concerns about the Yersinia pestis bacterium, responsible for millions of deaths in the Middle Ages. The case, reported by the Flagstaff Medical Center, involved a patient infected with the bacterium, which still circulates among wild rodents in some regions of the world. In Brazil, the last case occurred in 2005 in Ceará, and experts assure that the risk of an epidemic is low but emphasize the need for epidemiological surveillance. The disease, treatable with antibiotics, does not pose a pandemic threat but requires early diagnosis.
The Yersinia pestis bacterium is primarily transmitted by fleas from rodents, such as squirrels and marmots, and persists in rural or wilderness environments. Sporadic cases still occur globally, with around 1,000 to 2,000 cases annually. In Brazil, areas in the Northeast, like Ceará, have recorded cases in the past, but active surveillance has kept the disease under control.
The Arizona death, though isolated, has reignited discussions about the importance of prevention and monitoring zoonotic diseases. Experts highlight that modern urban conditions hinder the bacterium’s spread, but the risk is never zero.
- Transmission factors: The disease spreads through bites from infected fleas or, rarely, contact with respiratory secretions.
- Effective treatment: Antibiotics like doxycycline and gentamicin cure most cases if administered promptly.
- Surveillance in Brazil: Rural areas in the Northeast are continuously monitored due to susceptible rodents.
- Global cases: Madagascar and parts of Asia also report sporadic occurrences.
Controlled risks, but vigilance is essential
The U.S. case, though tragic, does not signal an imminent epidemic risk, according to infectious disease specialists. Yersinia pestis does not adapt well to urban environments, where hygiene and pest control are more effective. In Brazil, the absence of human cases since 2005 reinforces the effectiveness of surveillance measures.
Alexandre Naime Barbosa, an infectious disease specialist from Unesp, explains that the bacterium survives in wildlife cycles involving rodents and their fleas. “Brazil lacks significant endemic reservoirs, which reduces the likelihood of outbreaks,” he states. He notes that the pneumonic form, more severe, requires close contact and is rare.
Monitoring in rural areas, especially in the Northeast, is well-established. In the 1990s, an outbreak in Ceará recorded 250 cases, but swift public health actions prevented further spread. Today, mandatory reporting and rapid diagnostic tests ensure immediate responses to any suspicion.
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- Risk areas: Rural regions in the Northeast, such as Ceará, are continuously monitored.
- Early diagnosis: Rapid tests identify the bacterium within hours.
- Prevention: Rodent and flea control is critical to preventing new cases.
History of the disease in Brazil
The Black Death left a profound mark on world history, but its incidence in Brazil has always been limited. Cases in the 1970s and 1980s, mainly in the Northeast, occurred in rural areas with abundant wild rodents. The last confirmed case, in 2005, involved a patient in Pedra Branca, Ceará, who recovered after treatment.
In the 1990s, a small-scale outbreak prompted action from health authorities. Swift intervention with antibiotics and vector control prevented the disease from spreading. Since then, Brazil has maintained strict protocols for monitoring zoonotic diseases, including bubonic plague.
Hélio Bacha, from the Albert Einstein Israelite Hospital, reinforces that modern conditions, such as sanitation and access to medication, make an epidemic unlikely. “Urban plague, common in the Middle Ages, lacks favorable conditions today,” he explains.
Clinical forms and symptoms
Yersinia pestis can manifest in three main forms: bubonic, septicemic, and pneumonic. The bubonic form, the most common, causes swollen lymph nodes, fever, and chills. Untreated, it can progress to the septicemic form, a generalized infection, or the pneumonic form, which affects the lungs.
The pneumonic form is the most dangerous, with up to 100% lethality without medical intervention. Its symptoms include coughing up blood, breathing difficulties, and high fever. However, early antibiotic treatment drastically reduces risks.
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Raquel Stucchi, from Unicamp, emphasizes the importance of rapid diagnosis. “Clinical suspicion should prompt immediate antibiotic use, even before lab confirmation,” she says. This protocol saved the patient in Brazil’s 2005 case.
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- Main symptoms: Fever, chills, swollen lymph nodes (bubonic), or bloody cough (pneumonic).
- Treatment: Antibiotics like streptomycin and doxycycline are effective.
- Lethality: Without treatment, the pneumonic form can be fatal within days.
- Diagnosis: Molecular tests identify the bacterium quickly.
Global prevention and control
The Black Death, despite its historical impact, is now a controllable disease. The lack of an effective vaccine prevents total eradication, but preventive measures, such as rodent and flea control, are highly effective. In endemic regions like the southwestern U.S. and Madagascar, surveillance programs monitor wildlife.
In Brazil, epidemiological surveillance is coordinated by bodies like the Ministry of Health and state departments. Rural areas are prioritized, focusing on identifying infected rodents and educating communities about prevention.
The Arizona death serves as a reminder of the importance of maintaining active surveillance systems. “The plague is not a threat from the past, but it’s also not an imminent risk,” explains Barbosa. “With vigilance and treatment, it remains under control.”
Why the disease persists
The persistence of Yersinia pestis is tied to its ability to survive in natural reservoirs. Wild rodents, such as marmots and squirrels, sustain the bacterium in cycles independent of humans. Infected fleas transmit the disease by biting other animals or, rarely, humans.
In regions like Madagascar, sporadic outbreaks occur due to poor sanitation. In the U.S., the Southwest is an endemic area with small-scale annual cases. In Brazil, the absence of significant reservoirs reduces the risk, but the possibility of imported cases requires vigilance.
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- Natural reservoirs: Wild rodents are the primary hosts of the bacterium.
- Transmission: Infected fleas are the main vector.
- Risk factors: Contact with wild animals in endemic areas.
- Control: Wildlife monitoring and sanitation are key measures.
Advances in diagnosis and treatment
Diagnosis of the plague has advanced significantly since the Middle Ages. Molecular tests, such as PCR, identify Yersinia pestis within hours, enabling rapid treatment. Antibiotics like gentamicin and doxycycline are effective in most cases, with cure rates near 100% when administered early.
Global surveillance systems track cases in real time. In Brazil, mandatory reporting ensures immediate investigation of any suspicion.
Bacha notes that the lack of a vaccine is the main barrier to eradication. “If we had an effective vaccine, we could eliminate the plague, but that hasn’t been achieved yet,” he says.
Lessons from the U.S. case
The Arizona case underscores the importance of robust health systems. The rapid identification of the patient and confirmation of the bacterium by the Flagstaff Medical Center demonstrate how surveillance can contain the disease. In Brazil, the experience with past cases, like the one in 2005, shows the effectiveness of current measures.
Experts agree that the Black Death, though historically significant, is not a pandemic threat in the modern world. However, its persistence in natural reservoirs requires ongoing monitoring. “Surveillance is the key to avoiding surprises,” says Stucchi.
The combination of rapid diagnosis, effective treatment, and prevention keeps the disease under control, but attention to zoonotic diseases must never waver.
