A child in Idaho contracted the plague — and authorities aren’t sure where he or she was exposed to the extremely rare and potentially killer disease.

The unidentified child from Elmore County could have become infected in their home state or during a recent trip to Oregon, the Central District Health Department said in a statement on Tuesday.

The young patient is recovering, according to officials, who didn’t release the child’s gender or age.

The disease, caused by the bacterium Yersinia pestis, is often associated with the “Black Death” epidemic that was spread by rats and killed millions in medieval Europe. This strain of bacteria still occurs naturally in some rodent populations, spread by fleas in rats and squirrels, but is exceedingly rare in humans.

Occasionally some humans do get infected with Yersinia pestis, usually through a flea or animal bite, according to Health.com. Person-to-person transmission is extremely rare, and wasn’t a factor in this case, officials said.

The last urban plague epidemic in the US happened in Los Angeles in 1924, when 30 people died, and since then, the disease has been scattered in rural areas on the west side of the country.

Since 1990, there have been two cases of plague in humans in Idaho and eight in Oregon.

About seven people in the US are infected every year, usually after being bitten by a flea or infected animal, according to the CDC.

Modern antibiotics can treat the plague, but if they’re not administered quickly, it can lead to death, according to the Centers for Disease Control and Prevention.

Symptoms can include fever, chills, headaches and weakness. In most cases, there’s also a painful swelling of the lymph nodes in the groin, armpit and neck.

People can protect themselves when visiting plague-infested wildlife areas by wearing insect repellent, long pants and socks.