What to know about human plague after a suspected case in Colorado

An average of seven human plague cases are reported each year in the United States, according to the Centers for Disease Control and Prevention, with most cases occurring in the West, especially in northern New Mexico and in Arizona.

In February, a case of human plague was confirmed in rural Oregon. The unnamed person there was thought to have been infected by a pet cat, which had symptoms, health officials said. The case was identified and treated early, “posing little risk to the community.”

What is the plague, and how does it spread?

The plague is caused by a zoonotic bacteria known scientifically as Yersinia pestis. It is transmitted by fleas and cycles naturally among wild rodents.

Bubonic plague, the most common form, is characterized by painful swollen lymph nodes or “buboes.” The bacteria multiply in a lymph node, close to where they entered the human body following a flea bite, and can spread in the bloodstream if untreated.

Other symptoms can include a sudden fever and chills, severe headaches, muscle aches, nausea and vomiting, according to the Colorado health department. Symptoms generally develop after an incubation period of one to seven days, the WHO says.

Plague occurs naturally and can infect humans and their pets. People can get plague from the bites of infected fleas, by touching infected animals or by inhaling droplets from the cough of an infected person or animal. “We advise all individuals to protect themselves and their pets from plague,” the Colorado health department said in a statement.

What’s the treatment for plague?

“Plague can be treated successfully with antibiotics, but an infected person must be treated promptly to avoid serious complications or death,” said Alicia Solis, program manager at the Pueblo Public Health Department.

Plague can be a severe disease in humans and fatal if untreated. “If plague patients are not given specific antibiotic therapy, all forms of plague can progress rapidly to death,” according to the CDC.

Usually, patients will have blood and other samples, such as sputum or pus, taken from a bubo. If the plague is identified, then antibiotics are administered as the usual treatment, and the patient may be medically isolated. “Early diagnosis and early treatment can save lives,” according to the WHO.

There is no commonly available vaccine for the plague. Improved sanitation and better living conditions and health care have helped to temper the disease.

The bubonic plague wiped out tens of millions of people in Europe in the 14th century — earning it the label Black Death. A handful of cases arise each year in the United States and around the world, though the disease is far less common and far more treatable today with antibiotics.

Between 1900 and 2012, there were 1,006 confirmed or probable human plague cases in the United States, according to the CDC. Bubonic plague accounts for over 80 percent of U.S. plague cases.

Plague can occur in rural and semirural areas of the Western United States, “primarily in semiarid upland forests and grasslands where many types of rodent species can be involved,” according to the CDC. Many types of animals can be affected by plague, including rock squirrels, wood rats, ground squirrels, prairie dogs, chipmunks, mice, voles and rabbits.

The last urban outbreak of rat-associated plague in the United States occurred in Los Angeles in 1924-1925, the CDC said.

Worldwide, since the 1990s, plague cases have mostly occurred in Africa, according to the WHO. The three most endemic countries are the Democratic Republic of Congo, Madagascar and Peru, it says.

According to the Pueblo County Public Health Department, there are several ways to prevent contracting or spreading plague, including:

• Eliminate places that rodents can hide and breed around your home, garage, shed or recreation area.
• Avoid contact with dead animals.
• Treat dogs and cats for fleas regularly. Flea collars have not been proved effective.
• Do not allow pets to hunt or roam in areas with rodents, such as prairie dog colonies.
• Keep pet food in rodent-proof containers.
• If you develop symptoms of plague, see a health-care provider immediately.