Public health officials in Colorado have confirmed a human case of bubonic plague, which is caused by the bacterium Yersinia pestis. The individual lives in Pueblo County, roughly 100 miles south of Denver.

The person was hospitalized but is recovering.

Bubonic plague is transmitted by fleas and the Centers for Disease Control and Prevention says it “cycles naturally among wild rodents,” including rats and prairie dogs, among others. The bacteria, which is transmitted by a flea bite or by handling an infected animal — including sometimes cats — is endemic in the Southwest. The source of the infection isn’t known.

About seven cases a year are diagnosed in the United States.

Once known as the “Black Death” because of its deadly toll in Europe where it killed millions in the Middle Ages, bubonic plague can be treated effectively with antibiotics if it’s diagnosed early and an appropriate antibiotic is administered quickly.

Signs, treatment of bubonic plague

According to the CDC, there are different forms of the same bacteria-caused plague, depending on where the infection settles in. Symptoms include fever, headache, chills, nausea, vomiting and weakness. With bubonic plague, patients also develop at least one swollen, painful lymph node. It takes between two and eight days after being bitten for the bacterial illness to develop.

“The bacteria multiply in a lymph node near where the bacteria entered the human body,” the CDC notes. “If the patient is not treated with appropriate antibiotics, the bacteria can spread to other parts of the body.”

This form of plague takes its name from those swollen lymph nodes in the armpits, neck and groin, which are called buboes, according to the Mayo Clinic.

Pneumonic plague settles in the lungs. Septicemic plague infects the blood.

The World Health Organization reports that “plague can be a very severe disease in people, with a case-fatality ratio of 30% to 60% for the bubonic type, and is always fatal for the pneumonic kind when left untreated.”

Because antibiotics are effective against plague, it’s important to be diagnosed and treated as soon as possible, WHO warns.

The CDC article notes that “During plague epizootics, many rodents die, causing hungry fleas to seek other sources of blood. People and animals that visit places where rodents have recently died from plague are at risk of being infected from flea bites. Dogs and cats may also bring plague-infected fleas into the home. Flea bite exposure may result in primary bubonic plague or septicemic plague.”

People can also be infected by contact with fluid or tissue that harbors the bacteria, or from humans and animals that have plague pneumonia that causes them to cough, allowing plague into the air. “Typically, this requires direct and close contact with the person or animal with pneumonic plague,” the article said.

That’s also the only mechanism for person-to-person spread — something not seen in the U.S. since 1924.


According to USA Today, “Most human cases in the U.S. have occurred in the Southwest — in northern New Mexico, northern Arizona and southern Colorado — and the West — in California, southern Oregon and far western Nevada.”

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But the bacteria is found in every country with the exception of Oceania, the cases more common in the Democratic Republic of Congo, Madagascar and Peru. “In Madagascar, cases of bubonic plague are reported nearly every year, during the epidemic season between September and April,” per WHO.

The article said a man in New Mexico died from bubonic plague in March and in February a case was identified in Oregon. An infected pet cat was likely the source in the Oregon case.

Staying safe

The Pueblo Department of Public Health and Environment in a news release explained precautions to take to avoid bubonic plague:

  • Get rid of nearby places where rodents can hide and breed by clearing brush, rock piles, trash and stacks of lumber.
  • Don’t touch dead animals without taking steps that include spraying yourself with insect repellent, then using a long-handled shovel to place the animal in a garbage bag, which should then be placed in an outdoor garbage container.
  • For insect repellent, use some that contains 20% to 30% DEET, which repels fleas. Treat pants, socks, shoe tops, arms and legs.
  • Don’t sleep with pets and treat cats and dogs regularly for fleas. The release said flea collars don’t really work.
  • Keep pets away from rodent areas.
  • Store pet food in rodent-proof containers.
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