Recent international headlines regarding a fatal plague case in Siberia have drawn global attention to a disease frequently relegated to history books, but public health officials emphasize that outdoor enthusiasts do not need to look across the globe to find potential exposure risks. Yersinia pestis, the bacterium responsible for historical and modern plague infections, remains actively circulating in wildlife and vector populations across the American West. As millions of people head outdoors for hiking, camping, and recreation, health agencies and land managers are underscoring the importance of understanding how the disease operates and what practical steps can minimize the risk of encounter.
The recent tragedy in Russia—where a laboratory worker died from a suspected pneumonic plague infection after handling a test tube containing the pathogen—prompted international authorities, including the European Centre for Disease Prevention and Control, to monitor the situation closely. While laboratory-acquired infections are extraordinarily rare, the incident serves as a stark reminder that Yersinia pestis is still very much present in natural ecosystems. In North America, the pathogen is endemic to specific wildlife and sylvatic systems. According to data from the Centers for Disease Control and Prevention (CDC), an average of five to seven human plague cases are diagnosed annually in the United States, typically concentrated in western states such as New Mexico, Arizona, Colorado, California, Oregon, and Nevada.
The vast majority of these domestic cases manifest as bubonic plague. Although bubonic and pneumonic infections are caused by the exact same bacterium, they differ significantly in how they enter the human body, how they progress, and how they are transmitted from one host to another.
What Is the Plague?
The historical footprint of the disease looms large in human memory. During the 14th century, the devastating pandemic known as the Black Death claimed the lives of between 75 and 200 million people worldwide, leaving an indelible mark on global history. However, public health experts stress that the plague is far from a relic of the past; it is a persistent, modern zoonotic disease that continues to occur sporadically in regions where wild rodent populations harbor the bacteria.
Recent years have underscored this ongoing reality across the western United States. In June 2026, the New Mexico Department of Public Health reported that a woman in her fifties died from the disease. This followed a fatal case of pneumonic plague in an Arizona man in July 2025, alongside two additional New Mexico residents who contracted infections that same year. Looking back further, public health records show a consistent trickle of cases: in January 2024, a 73-year-old man in rural America was diagnosed with bubonic plague after coming into contact with an infected cat, while a Colorado man contracted the disease via a flea bite during the same period. Another New Mexico man also succumbed to the illness that year.
These modern incidents frequently mirror well-documented historical cases, such as the widely publicized 2013 account profiled by Outside magazine detailing the harrowing survival of Paul Gaylord, an Oregon man who contracted the plague from his sick domestic cat and endured a prolonged, life-threatening medical battle.
How Do Hikers Encounter the Plague?
For those who enjoy spending time on public lands, encounters with Yersinia pestis typically occur through intermediate vectors rather than direct contact with infected humans. Hikers, campers, and backpackers can become infected when they are bitten by an infected flea. These fleas commonly parasitize wild rodents—such as ground squirrels, chipmunks, woodrats, and prairie dogs—and can easily jump to humans or domestic pets that venture too close to rodent burrows or resting areas.
Furthermore, domestic animals like dogs and cats that accompany their owners into the backcountry can act as accidental vectors for the disease. Pets allowed to roam off-leash can investigate wild rodent carcasses or bring infected fleas back into family tents, vehicles, and homes, thereby increasing the risk of transmission to human handlers.
Within the natural environment, the bacterium drives what scientists refer to as sylvatic plague—a flea-borne bacterial disease that periodically sweeps through wildlife populations. During localized outbreaks in the American West, sylvatic plague has been documented to kill up to 100 percent of infected prairie dog colonies, according to the Morris Animal Foundation. These massive die-offs not only disrupt local ecosystems and food webs, but they also elevate the immediate risk of infection as hungry, displaced fleas abandon cooling carcasses and seek alternative hosts, which can include passing hikers, livestock, domestic pets, and other wildlife.
Early Symptoms and Risk
Understanding how the disease attacks the human body is critical for recognizing early warning signs and seeking prompt medical intervention. Both bubonic and pneumonic plagues stem from Yersinia pestis, but their clinical presentations diverge based on the route of exposure. Pneumonic plague is primarily transmitted when an individual inhales infectious respiratory droplets, a route that can also facilitate human-to-human transmission under specific circumstances. Conversely, bubonic plague spreads predominantly through the bites of infected fleas or through direct handling of infected animal tissues.
According to guidelines from the Colorado Department of Public Health and Environment, the incubation period for plague typically ranges from two to seven days following exposure. Early symptoms can mimic a severe flu and often include a sudden onset of fever, chills, severe headache, generalized body aches, abdominal pain, weakness, and, in advanced or secondary stages, pneumonia and cardiovascular shock.
Bubonic plague remains the most frequently diagnosed form of the disease in the United States. It is clinically characterized by the rapid development of extremely painful and swollen lymph nodes, known as buboes, which typically appear within 24 to 48 hours of the initial bite as the bacteria migrate to the nearest lymph node.
Because plague is caused by a bacterium, infections can be successfully treated with common antibiotics, but early diagnosis is paramount. Left untreated, the disease can rapidly progress to severe systemic illness or prove fatal, making swift medical evaluation essential for anyone experiencing suspicious symptoms after visiting rural or wilderness areas in the West.
How to Stay Safe on the Trail
As outdoor recreation continues to draw millions of visitors to public lands, land management agencies and public health departments emphasize that simple, proactive measures can significantly reduce the likelihood of encountering the pathogen. The National Park Service advises outdoor enthusiasts to maintain a safe and respectful distance from all wild animals, particularly rodents that appear sluggish, sick, or dead.
For dog owners and hikers utilizing shared trails, keeping pets securely leashed prevents animals from chasing wildlife, digging into rodent burrows, or investigating carcasses. Additionally, ensuring that pets are kept strictly up-to-date on veterinarian-recommended flea and tick prevention medications creates an essential chemical barrier, stopping insects from using household pets as a bridge into human living spaces.
Personal protection measures are equally effective. Applying insect repellents containing active ingredients such as DEET or Picaridin to exposed skin, lower legs, and clothing can deter fleas and ticks while navigating high-risk brush or grassland environments. By combining situational awareness with basic preventive habits, outdoor enthusiasts can continue to explore the backcountry safely while remaining mindful of the natural ecosystems and endemic pathogens that share the western landscape.
