It sounds like a punchline or a plot point from a gritty HBO show. You’re hiking through the Sierra Nevadas or maybe just walking your dog in a dusty Colorado suburb, and suddenly there’s a warning sign about Yersinia pestis. The Black Death. In the 21st century. It feels impossible, right? We have iPhones and SpaceX, yet we’re still dealing with the literal plague in the US.
But it’s real.
Most people think the plague vanished after it wiped out half of Europe in the 1300s. It didn't. It just moved. Every year, a handful of Americans—usually between five and fifteen people—contract the plague. It’s not an urban myth. It’s a biological reality of the American West.
How the Plague Actually Got to America
The United States didn't always have this problem. We imported it.
Back in 1900, rat-infested steamships from Asia docked in San Francisco. The bacteria hopped off the ships via fleas and immediately found a new home in the local rat population of Chinatown. The city’s response was, frankly, a mess. Authorities initially denied it existed because they were terrified of the "plague" label hurting trade. They even tried to wall off parts of the city. By the time they took it seriously, the bacteria had already jumped from urban rats to native rural rodents like ground squirrels and prairie dogs.
That was the turning point. Once it hit the wild rodent population, it became endemic. You can't vaccinate every squirrel in the Rockies.
The bacteria moved East, stopping roughly at the 100th meridian. Today, if you look at a map of plague cases provided by the Centers for Disease Control and Prevention (CDC), it’s almost entirely concentrated in the "Four Corners" region—Arizona, New Mexico, Colorado, and Utah—along with California, Oregon, and western Nevada. New Mexico is often the hotspot. The landscape there is just perfect for the flea-rodent cycle to thrive.
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It’s Not Just One Type of Sickness
When people talk about the plague in the US, they usually mean Bubonic plague. This is the one where your lymph nodes—usually in the groin or armpit—swell up into painful "buboes." It’s nasty. It’s painful. But if you catch it early, modern antibiotics like streptomycin or gentamicin knock it out pretty effectively.
Then there’s Septicemic plague. This happens when the bacteria multiply directly in your bloodstream. This is the scary one. It can cause skin and other tissues to turn black and die, especially on your fingers, toes, or nose. That’s where the "Black Death" name comes from.
The rarest and most dangerous version is Pneumonic plague. This is the only form that can spread from person to person through cough droplets. If you have this, you’re basically a walking biohazard. In the US, this is incredibly rare, but it’s the reason health officials freak out and start contact tracing the second a case is confirmed.
The Wildlife Connection: Why You Should Fear the Prairie Dog
You see a prairie dog. It’s cute. It barks. You want to feed it a cracker.
Don't.
Prairie dogs are highly susceptible to plague. In fact, biologists often find "plague die-offs" where entire colonies are wiped out in days. If you’re hiking and you see a bunch of dead rodents, or a colony that seems strangely silent, turn around. The fleas that lived on those rodents are now hungry. Since their original host is dead, they are looking for the next warm body. That could be you. Or it could be your dog.
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Domestic cats are actually a huge risk factor too. Cats are highly susceptible to the plague and can develop the pneumonic version. If your outdoor cat catches an infected mouse and then comes home to cough on you, you’ve got a massive problem. In 2014, Colorado saw a small outbreak linked to a single dog; four people ended up getting sick. It was a wake-up call for veterinarians across the West.
Why Does It Still Persist?
Climate plays a huge role. Studies by researchers like Dr. Kenneth Gage, a world-renowned plague expert formerly with the CDC, have shown that cooler summers and wetter winters in the Southwest lead to more vegetation. More food means more rodents. More rodents mean more fleas. More fleas mean a higher chance of Yersinia pestis spilling over into the human population.
It’s a delicate ecological dance.
Honestly, the risk to the average person is statistically tiny. You’re more likely to be struck by lightning than to die of the plague in the US. But that doesn't mean we can be complacent. The bacteria is a survivor. It can live in the soil. It can hide in the burrows of hibernating animals. It’s patient.
The Reality of Treatment Today
If you get the plague today, you aren't going to be hauled away in a cart while someone yells "bring out your dead."
You’ll be put in an isolation ward. You’ll be pumped full of IV antibiotics. The mortality rate for untreated bubonic plague is around 50% to 60%, but with modern medicine, that drops significantly. The key is speed. The symptoms—fever, headache, chills—look exactly like the flu. Many people ignore it for a day or two. With plague, you don't have a day or two to waste.
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Doctors in New Mexico are trained to look for this. A doctor in New York City? Maybe not. That’s why travel history is so vital. If you’ve been camping in Santa Fe and you start feeling like death warmed over, you need to tell your ER doctor exactly where you were.
Common Misconceptions
People think the plague is a disease of the poor or the "unclean." That’s nonsense. In the US, cases often pop up in affluent mountain communities or among hikers and outdoorsy types. The bacteria doesn't care about your tax bracket; it cares about how close you are to a flea-ridden squirrel.
Another myth: that we can just eradicate it. We can't. To get rid of the plague, we’d have to sterilize the entire ecosystem of the American West. It’s part of the landscape now, just like hantavirus or Lyme disease.
Staying Safe in Plague Country
You don't need to live in fear, but you do need to be smart. If you live in or visit the Western US, there are basic, non-negotiable rules for dealing with the potential of plague.
- Protect your pets. Use flea control products religiously. If you live in a plague-prone area, don't let your dogs or cats roam free in areas with high rodent populations.
- Don't feed the wildlife. Seriously. Keeping squirrels or chipmunks around your campsite or backyard is just asking for trouble.
- Use insect repellent. If you’re hiking or camping, use a repellent that contains DEET. It works on fleas just as well as mosquitoes.
- Rodent-proof your home. Don't leave piles of wood or junk near your house where mice can nest. Keep your trash tightly sealed.
- Wear gloves. If you’re a hunter or someone who has to handle dead animals, wear gloves. The bacteria can enter through small cuts in your skin.
The plague in the US is a reminder that nature is never truly "conquered." We’ve managed to keep it at bay through sanitation and medicine, but it’s always there, humming along in the background of the high desert and the mountain forests. Respect the distance between yourself and the wild, and you’ll be fine.
Actionable Steps for Travelers and Residents
- Check the Maps: Before heading on a long-term camping trip in the West, check the local health department websites for recent plague activity or "die-off" reports.
- Identify Symptoms: If you develop a sudden, high fever and swollen glands after being outdoors in the West, seek medical attention immediately. Don't wait for a rash or "black spots."
- Veterinary Vigilance: If your pet becomes lethargic with a fever after being outside in a rural area, tell your vet you're concerned about plague. It could save your life and theirs.
- Report Die-offs: If you see an unusual number of dead rodents in a specific area, notify the state wildlife agency. They use these reports to track the movement of the disease.