For many people, hearing about the bubonic plague might immediately bring to mind images of medieval epidemics and the socalled Black Death. Yet, despite its historical reputation, this bacterial disease has not disappeared from the modern world. In fact, the question of whether the bubonic plague is present in Colorado today has surfaced repeatedly, especially in recent years as health officials monitor animal and occasional human cases. Understanding whether the bubonic plague is in Colorado requires looking at current public health data, how the disease spreads, and what the risks are for residents and visitors in the state.
What Is the Bubonic Plague?
The bubonic plague is caused by the bacteriumYersinia pestis. This bacterium can infect humans and animals, and it is most commonly transmitted through the bite of infected fleas. These fleas often live on rodents such as prairie dogs, rock squirrels, ground squirrels, mice, and other small mammals. If a flea carrying the bacteria bites a human or pet, the infection can be passed on. Symptoms of bubonic plague typically include sudden fever, chills, headache, muscle aches, and painful, swollen lymph nodes known as buboes. If treatment with antibiotics is delayed or not provided, the disease can become severe and lifethreatening.
Plague in the United States and Colorado
The bubonic plague is rare in the United States, but it has not been completely eradicated. According to national health data, an average of about seven human plague cases are reported in the U.S. each year. Many of these occur in the western states, including areas of Colorado. The Centers for Disease Control and Prevention (CDC) identifies northern New Mexico, northern Arizona, and southern Colorado as regions where plague activity has historically been reported. Cases in the U.S. are typically scattered and occur most often in rural areas rather than urban centers.
Colorado’s Plague Activity
In Colorado, health authorities regularly monitor plague activity among wildlife and occasional human cases. Plague circulation in animals and fleas has been observed for decades, and monitoring helps officials track where the bacteria may be present. In recent years, there have been reports of plague activity in rodents and other wildlife within the state. This includes positive tests in animals such as rodents and warnings issued to the public during periods of detected activity. Public health departments emphasize that seeing plague in wildlife does not mean a widespread outbreak, but it does mean that the bacteria are present in nature.
Human Cases of Bubonic Plague in Colorado
Although rare, human cases of plague do occur in Colorado. In 2025, the Colorado Department of Public Health and Environment reported multiple human plague cases, including a resident diagnosed with the infection. These cases were linked to exposure to sick animals such as rodents or their fleas, and there was no evidence of widespread transmission from person to person. Officials also noted that such cases are uncommon and that the risk to the general public remains low. In the past decade, Colorado has reported only a small number of human plague cases, with some years having no reported infections at all.
Historical Incidents
Historically, Colorado has seen plague activity in both animals and people. For example, back in 2023 and 2021, health reports identified human plague cases in Montezuma County and La Plata County, respectively. These cases were linked to exposure through infected fleas or contact with sick animals, highlighting the importance of awareness and precaution when in areas with known wildlife plague activity. However, these incidents remain rare and have not led to widespread outbreaks.
Why Plague Still Exists in Colorado
The bubonic plague persists in Colorado and other western states because certain rodent populations naturally carry the bacterium in their blood systems. Fleas feeding on these rodents can become infected and then pass the bacteria along to other animals, pets, or occasionally humans. Because of this cycle, health officials expect to find positive plague tests in wildlife during certain seasons, particularly in spring and summer when flea activity increases. Although it may sound alarming, this natural reservoir of the bacteria is wellknown to scientists and public health authorities, and regular surveillance helps keep people informed and safe.
Transmission and Risk Factors
Transmission of plague to humans typically requires close contact with infected fleas or animals. Touching sick or dead animals, allowing pets to roam in wild rodent habitats, or being bitten by an infected flea are common pathways for transmission. Persontoperson transmission of bubonic plague is extremely rare and generally does not occur without the pneumonic form of the disease, which involves the lungs and respiratory droplets. Public health experts stress that avoiding contact with wildlife and protecting pets from fleas significantly reduces the risk of infection.
Precautions and Public Health Advice
Colorado health officials provide guidance on how residents and visitors can protect themselves and their pets from plague. First and foremost, avoiding direct contact with wildlife, especially rodents and rabbits, helps reduce risk. Using flea prevention products on pets and keeping them away from wild rodent habitats are key measures. If you visit areas with known rodent populations, using insect repellent, wearing long clothing to minimize skin exposure, and being attentive to dead animals in the area can help lower the chance of flea bites. Monitoring local health alerts and staying informed about seasonal plague activity also supports public safety.
Symptoms and Seeking Medical Care
If a person is exposed to plague and begins to experience symptoms such as fever, chills, fatigue, muscle aches, or swollen lymph nodes, seeking medical attention promptly is crucial. Early diagnosis and treatment with antibiotics can successfully cure plague in most cases. Delayed treatment could lead to more severe forms of the disease or complications. Because plague is treatable with modern antibiotics, health officials emphasize that awareness and timely care are effective at preventing serious outcomes.
Public Perception vs. Reality
The idea that bubonic plague is in Colorado can feel alarming to many people, particularly when news reports highlight specific cases in animals or humans. However, it’s important to understand that such cases are unusual and closely monitored by public health authorities. Plague activity in wildlife does not automatically translate into widespread infection risk for the broader public. Instead, the bacteria’s continued presence in natural rodent populations represents a known and managed health concern rather than an epidemic scenario. This subtle distinction helps temper fear with factual risk assessment.
Summary of Current Situation
Yes, the bubonic plague is present in Colorado in terms of occasional wildlife cases and rare human infections. The disease continues to circulate among rodents and fleas in parts of the state, and human cases do occur sporadically. However, the overall risk to the public remains low, and with proper precautions and awareness, individuals can greatly reduce their chances of encountering the disease. Public health authorities remain vigilant in monitoring plague activity and educating residents about safety measures, ensuring that isolated cases do not lead to larger problems.
The bubonic plague has not disappeared from the modern world, and Colorado is one of several western states where the bacterium that causes it continues to exist in wildlife. Occasional reported cases of plague in rodents, pets, and even humans underscore the importance of awareness and prevention. While rare, these cases do occur because the disease naturally persists in certain animal populations and their fleas. Thanks to modern medical care and public health monitoring, the threat to human life is much lower today than in past centuries. By understanding the risk factors, recognizing symptoms, and following public health recommendations, residents and visitors to Colorado can stay safe while enjoying the outdoors in areas where plague activity may be present.