Known around the world for killing tens of millions of people in Europe during the Black Death in the Middle Ages, the plague is back in the headlines after cases were detected in the United States.
Health officials in the state of Colorado have just confirmed a human case of the infamous but rare bacterial infection, which today is easily treated with antibiotics.
The US Centers for Disease Control and Prevention (CDC) estimates there are seven human cases of plague per year in the US, and in February, Oregon officials reported it in a person who likely got it from their sick cat.
Surprised to hear the plague is still around? Here's what you need to know.
What is the plague?
The bubonic plague is the most common form of the bacterial infection, which spreads naturally among rodents like rats.
There are two other forms of the plague: septicemic plague (which spreads through the whole body) and pneumonic plague (which infects the lungs).
Bubonic plague causes painfully swollen lymph nodes that are most commonly found in the groin, armpit, and neck, called buboes. It will often advance and turn into the other two forms of plague if untreated.
Other symptoms of the plague include sudden high fever and chills, headaches, and pain in the abdomen, legs, and arms, according to the Cleveland Clinic.
How do you get it?
The bacteria is transmitted through the bites of infected fleas, which spread it between rodents, pets, and humans.
People can also get plague through touching infected bodily fluids, so health experts recommend taking extra care when handling dead or sick animals. The plague can also spread through the respiratory droplets of a patient who has pneumonic plague.
Pneumonic plague is the most deadly and easiest to spread, with a nearly 100 per cent fatality rate untreated, said Lisa Morici, a microbiologist and immunologist at the Tulane University School of Medicine.
Where are cases of the plague most common?
In the US, most cases happen in rural areas of northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and far western Nevada, according to the CDC.
Worldwide, plague is found the most in Congo, Madagascar, and Peru, according to the World Health Organization (WHO).
According to the European Centre for Disease Prevention and Control (ECDC), plague has been absent from Europe for over half a century.
How is the plague treated?
The plague was never eradicated, but we've gotten better at preventing its spread and treating it in humans.
When treated early with antibiotics, the plague can be cured. The key is to get to a doctor fast - otherwise the plague can be deadly.
And, as the old adage goes, prevention is better than a cure.
Keeping areas around the home clear of debris and other things that can attract rodents can lower the risk of infection, as can making sure pets are up to date on flea treatments.
When hunting, camping, or otherwise spending time outdoors, the CDC recommends using a bug spray with DEET to keep fleas and other disease-spreading pests away.
Is there a plague vaccine?
Yes, but the WHO only recommends it for people who are at high risk of infection, like laboratory and health care workers. There's no plague vaccine available in the US or Europe.
Morici said there is need for more research, because while the vaccines used in other parts of the world work against bubonic plague, there isn't strong evidence to show they protect against the pneumonic form of plague.
Testing a plague vaccine would be ethically and logistically difficult, she said.
"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 — there's just not a huge market for a plague vaccine at this point in time," Morici said.
