Colorado still has plague, but is it the same as Russia's?

Here’s a twisted fact Coloradans love sharing with transplants and tourists to scare them away: Colorado wildlife can carry plague.

Yes, that plague. From the same family as the bubonic one, which ravaged the world in the 14th century and killed an estimated 200 million people.

So why aren’t we wearing masks and fighting boils, or living under quarantine, like some people currently are in Russia? Although some Colorado critters carry the scary bacteria that causes plague, we have plenty of good reasons not to panic. Here’s why.

Yersinia, what?

Plague, as we know it, is caused by a rod-shaped bacterium called Yersinia pestis. That bacterium can spread in multiple ways, causing various versions of the disease. During the Black Death in Europe, plague was spread by flea bites and had a high mortality rate. The disease has largely been eradicated outside of rare, localized outbreaks, but variants still pop up.

On Oct. 2, a 28-year-old Russian research worker died after being exposed to plague at a lab in Siberia, according to the World Health Organization. International media reports indicate this form of plague was pneumonic. It spreads from respiratory droplets into the lungs, with symptoms starting within 24 hours of exposure. It is fatal if not treated immediately.

The Russian government reportedly quarantined around 200 people around the facility, but has provided little information about the outbreak.

The last time someone died in the United States from pneumonic plague was in 2025 in Coconino County, Arizona, where a man had been working with sick cats. The time before that? Colorado in 2014.

“Plague is found in certain wild animals in Colorado, including rodents, squirrels, prairie dogs, chipmunks and rabbits,” Kelsey Campbell, spokesperson for Jefferson County Public Health, tells Westword. “People can be exposed to plague through infected fleas or animals, especially when spending time outdoors.”

Plague has been in the United States since 1900, arriving via rat-infested steamships and spreading to rural rodent species in the western part of the country. Since 1970, the Centers for Disease Control and Prevention has reported only two human cases of plague on the East Coast, but Colorado and New Mexico still see cases, especially among pets.

Most domesticated animals contract plague from wildlife or fleas. According to the Colorado Department of Health and Environment (CDPHE), there were six recorded cases of animal plague across the state from Jan. 1 to Oct. 12 of this year.

Colorado’s last human case of plague was in Pueblo County in 2024, but it was treated.

“In Pueblo County, plague is maintained in a rodent-flea cycle that can transmit to wild and domestic animals, and to humans. The most common animal species implicated in the transmission of plague to humans in Colorado are fleas, tree squirrels, ground squirrels (including prairie dogs), woodrats and domestic cats,” Trysten Garcia, a spokesperson for the Pueblo Department of Public Health and Environment, says.

Is Colorado’s plague the same as Russia’s?

While the bacteria found in Colorado and Russia is the same, the transmission cause is significantly different. Now that a human has the respiratory version, it could spread through droplets.

“While both situations involve the bacterium Yersinia pestis, the public health risk and context in Colorado is completely distinct from the recent event reported in Russia,” says Hope Shuler, spokesperson for CDPHE. “In Colorado, plague is rare but naturally occurring, and it has existed in the state since at least the 1940s. By contrast, the situation in Russia involves a potential isolated laboratory exposure. The risk to the general public in Colorado remains low and unchanged by the situation in Russia.”

Even with modern science, fully eradicating plague is nearly impossible without exterminating certain rodent species and the fleas. But for humans, it’s simple: don’t eat or touch rodents — or work in a plague factory.

Shuler says we can keep our pets safe with flea prevention medication, avoiding wild animals, and regular visits to the doctor and vet. Plague can be treated with antibiotics, but timing is crucial.

“Surveillance for plague in people and animals allows public health authorities to respond rapidly to cases to prevent further spread of the infection,” Shuler says. “Plague can be transmitted from human to human when the infection has caused pneumonia, but this is rare. Most people are exposed via flea bites or handling infected animals without appropriate protection such as gloves.”

Those prairie dogs aren’t so cute now, are they?

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Sage Kelley joined Westword as a staff writer in May 2026. He previously worked at the Denver Gazette, covering breaking news and Jefferson County. Sage has received numerous awards from the Society of Professional Journalists and Colorado Press Association for his reporting on arts and public safety. A Delaware native, Sage graduated from Pratt Institute in New York City with a major in creative writing.