In the 1300s, a bacterial infection killed tens of millions in Europe. The disease was known as the plague, sometimes called the Black Death. Last week, Colorado health officials reported a human case of the plague. Mercifully, antibiotics easily treat the once-dread disease today.
The last city-wide plague outbreak in the United States hit Los Angeles, California, in 1924. Historians say infected rats brought the disease on steamships.
Staff at the Centers for Disease Control and Prevention (CDC) estimate there are an average of seven human cases of plague per year in the United States.
In February, Oregon officials reported a different case in a resident who likely got it from a sick cat. The human survived. The cat did not.
Surprised to hear the plague is still around?
Dr. Dan Barouch heads the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, Massachusetts. He told CNN that plague still exists because of what he calls “an animal reservoir.”
He explains: “Because we can’t treat all animals in the wild, it persists in nature and thus occasionally causes a limited number of human cases.”
There are different presentations of the plague. The bubonic plague is the most common form of the infection. It spreads naturally among rodents like prairie dogs and rats.
Bubonic plague causes painfully swollen lymph nodes. The term for these nodes is buboes—hence the term “bubonic.” This form of plague will often turn into the other two forms of plague if untreated. The two other forms of the plague are septicemic (invades the bloodstream) and pneumonic (infects the lungs).
Other symptoms of the plague include sudden high fever and chills, headaches, and pain in the abdomen, legs, and arms.
The bacterium that causes plague spreads through the bites of infected fleas. These pesky insects transmit the bacteria among rodents, pets, and humans.
People can get plague by touching infected body fluids, such as saliva. So health experts recommend taking extra care when handling dead or sick animals. The plague can also spread through the respiratory droplets—cough, cough!—of a patient who has pneumonic plague.
Pneumonic plague is the most deadly and easiest to spread. Almost 100% of infected people die without treatment, says Lisa Morici, a microbiologist and immunologist.
In the United States, most plague cases occur in rural areas of northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and western Nevada, according to the CDC.
Worldwide, plague is found most often in Congo, Madagascar, and Peru, according to the World Health Organization.
Although the plague has never been eradicated, God has allowed humans to get better at preventing its spread and treating it in other humans.
When treated early with antibiotics, the plague can be cured. The key is to get to a doctor fast.
Methods for preventing plague include keeping areas around the home clear of debris and other things that can attract rodents. Making sure pets are up to date on flea treatments is important too. When hunting, camping, and spending time outdoors, the CDC recommends using a bug spray with DEET. It helps keep fleas and other disease-spreading pests away.
Morici says scientists need to do more plague research. She says vaccines used in other parts of the world work against bubonic plague. However, there isn’t strong evidence to show the medicines protect against the pneumonic form of plague.
She admits testing a plague vaccine would be difficult. After all, who would volunteer for plague exposure without a working vaccine?
At the end of the day, research may come down to a question of dollars.
“Because the bubonic form is quite treatable with antibiotics and also quite rare—you don’t see thousands and thousands of cases of plague a year,” Morici says. “There’s just not a huge market for a plague vaccine at this point in time.”
