Recent international headlines detailing a fatal plague case in Siberia have drawn renewed attention to a centuries-old disease, but public health officials and outdoor experts emphasize that travelers do not need to look across the globe to find the pathogen. Yersinia pestis, the bacterium responsible for both bubonic and pneumonic plague, remains actively circulating in wildlife populations across the American West. For hikers, campers, backpackers, and pet owners spending time on public lands, understanding where the disease persists and how it spreads is a vital component of outdoor safety.
The global conversation surrounding the pathogen intensified following reports that a laboratory worker in Russia died from a suspected pneumonic plague infection after handling a test tube containing the bacterium. In response to the tragedy, international health authorities, including the European Centre for Disease Prevention and Control, announced they are closely monitoring the situation. While laboratory-acquired infections are extraordinarily rare, the incident serves as a stark reminder that Yersinia pestis is still very much a living, breathing part of natural ecosystems—including those found throughout North America.
According to data compiled by the Centers for Disease Control and Prevention, an average of five to seven people contract plague infections every year in the United States. These cases are not randomly distributed nationwide; rather, they are largely concentrated in specific western states where the sylvatic cycle of the disease is well-established. New Mexico, Arizona, Colorado, California, Oregon, and Nevada report the vast majority of domestic cases. While infections can manifest in different ways, the vast majority of these U.S. cases present as the bubonic plague. Though bubonic and pneumonic infections are caused by the exact same bacterium, they differ significantly in how they invade the body, spread between hosts, and progress in severity.
What Is the Plague?
When people hear the word plague, they frequently think of the catastrophic pandemic of the 14th century. Known historically as the Black Death, the medieval pandemic killed between 75 and 200 million people across Europe, Asia, and North Africa, cementing its place as one of the most devastating public health disasters in human history. However, despite its association with ancient history, the plague is very much a modern disease that continues to occur in cycles across specific geographic niches.
The historical timeline of the disease extends well into the modern era, punctuated by sporadic domestic cases. In June 2026, the New Mexico Department of Public Health reported that a woman in her fifties died from the plague. That tragedy followed a series of other regional incidents. In July 2025, an Arizona man tragically died of pneumonic plague, while two other individuals in New Mexico were infected that same year.
The record shows a steady, albeit low-frequency, persistence of the illness. In January 2024, a 73-year-old man was diagnosed with the bubonic plague after coming into direct contact with an infected domestic cat. During the same period, a Colorado man contracted the disease via a flea bite, and another New Mexico man lost his life to the infection.
The danger posed by domestic animals acting as vectors has long been documented. In 2013, outdoor media outlets profiled the harrowing story of Paul Gaylord, an Oregon man who miraculously survived a severe plague infection after he was exposed while tending to his sick cat. These documented encounters highlight that human interactions with the disease typically happen at the intersection of wildlife habitats, domestic pets, and human recreation.
How Do Hikers Encounter the Plague?
Outdoor enthusiasts typically cross paths with Yersinia pestis through vectors residing in the wilderness. Hikers can become infected when they are bitten by an infected flea. These insects often live as parasites on wild rodents, such as ground squirrels, chipmunks, mice, and prairie dogs, but they can easily jump from wild hosts to humans or domestic pets wandering through the brush.
Dogs and cats that accompany their owners on outdoor adventures can inadvertently become vectors for the disease. Pets allowed to roam off-leash or investigate animal burrows can pick up infected fleas and bring them directly into tents, sleeping bags, and family vehicles, dramatically increasing the risk of transmission to humans.
In the wild, the disease manifests as sylvatic plague, a flea-borne bacterial infection that regularly sweeps through native animal populations. During intense regional outbreaks in the American West, the bacterium can kill up to 100 percent of infected prairie dog colonies, according to findings from the Morris Animal Foundation. These massive die-offs not only disrupt local ecosystems and food webs, but they also elevate the immediate risk of human exposure, as hungry fleas abandon dead hosts in search of new ones, increasing the likelihood that hikers, hunters, or campers might cross paths with the pathogen.
Early Symptoms and Risk
Though bubonic and pneumonic plagues stem from the exact same bacterium, the clinical presentation depends entirely on the route of transmission. Pneumonic plague is primarily transmitted through the inhalation of infectious respiratory droplets, a mechanism that can facilitate human-to-human transmission. Bubonic plague, by contrast, spreads almost exclusively through the bites of infected fleas or through direct contact with infected animal tissues.
Medical authorities, including the Colorado Department of Public Health and Environment, note that the incubation period for the plague can last up to a week following exposure. Early symptoms are frequently non-specific and flu-like, encompassing a sudden onset of high fever, severe headaches, abdominal pain, generalized weakness, and, in advanced stages, pneumonia and shock.
Bubonic plague remains the most frequently diagnosed form of the disease in the United States. It is classically characterized by the rapid development of painful, swollen inflammations of the regional lymph nodes, known as buboes, which typically appear within 24 to 48 hours of the initial infection. Because the bacterium multiplies rapidly within the lymphatic system, a plague infection can quickly become life-threatening and requires immediate, aggressive antibiotic treatment to ensure patient survival.
How to Stay Safe on the Trail
For those heading into the backcountry, avoiding the plague is largely a matter of practicing routine preventive hygiene and maintaining a healthy distance from wildlife. Public land management agencies, including the National Park Service, advise visitors to stay a safe distance from all wild animals, particularly rodents, and to refrain from feeding or touching wild mammals, whether they appear healthy or distressed.
Pet owners bear a special responsibility when recreating in endemic regions. Keeping dogs strictly leashed prevents them from exploring rodent burrows, investigating animal carcasses, or chasing wildlife. Furthermore, ensuring that both dogs and cats are kept continuously up-to-date on veterinarian-recommended flea and tick prevention treatments is essential for stopping parasites from hitching a ride back to civilization.
In addition to protecting pets, hikers can take personal protective measures by applying insect repellents containing DEET or Picaridin to exposed skin, lower legs, and clothing before stepping onto the trail. By combining vigilant pet management, personal insect protection, and a cautious approach to wildlife and animal remains, outdoor enthusiasts can continue to safely explore the public lands of the American West while minimizing their exposure to a resilient and ancient pathogen.
