CNN — A person in Deschutes County, Oregon, has been diagnosed with a case of bubonic plague, making them the state’s first confirmed case of this rare bacterial infection since 2015.

The person was probably infected by their cat, and “all close contacts of the resident and their pet have been contacted and provided medication to prevent illness,” Dr. Richard Fawcett, the Deschutes County health officer, said in a statement last week. Common antibiotics like gentamicin and fluoroquinolones are first-line treatment for plague, according to the US Centers for Disease Control and Prevention.

The infected person was “treated in the earlier stages of the disease,” according to the statement, and poses “little risk” to the community.

But the case is raising questions about how plague — best known for killing millions of people in Europe during the Middle Ages — can spread in the modern day.

“The reason why it hasn’t been eliminated is because there’s an animal reservoir. The bacteria can infect animals, and because we can’t treat all animals in the wild, it persists in nature and thus occasionally causes a limited number of human cases,” said Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, who is not involved in the Oregon case.

About seven human plague cases are reported each year in the United States, primarily in rural Southwest and Northwest areas, according to the CDC.

Plague is caused by the bacterium Yersinia pestis. Humans usually get it after being bitten by a flea that is carrying the bacterium or after encountering an infected animal. Symptoms typically emerge in humans about two to eight days after exposure, and they include painful, swollen lymph nodes, fever, headache, chills and weakness.

If the condition is not diagnosed early, it can progress to infections of the bloodstream or lungs, according to the statement from Deschutes County Health Services. Those severe forms of the disease are more difficult to treat.

But overall, “the plague is easily recognized, easily diagnosed and easily treated” with antibiotics nowadays, said Dr. Harish Moorjani, an infectious disease specialist at Northwell Health, who is not involved in the Oregon case.

Compared with the Middle Ages, “people should put everything into perspective; this is a different era,” he said.

Barouch thinks it is “very unlikely” that the plague will spread beyond the person in Oregon.

“As long as the person and their immediate contacts are treated — which did occur in this case — the chance it will spread any further is very, very low. So I think that people should not be worried, but if people want to reduce their risks, then they should avoid contact with rodents and fleas and sick animals,” he said.

“It turns out cats can be infected quite easily because cats have a difficult time controlling the bacteria themselves,” Barouch said. “Dogs can be infected too, but cats can be infected even more easily. Squirrels, chipmunks, rodents are typically the animals that are infected in the wild.”

In the Middle Ages, plague caused a pandemic called the Black Death and was thought to spread by fleas carried by rats.

“The reason why it caused such widespread death and destruction in the Middle Ages is because we didn’t have antibiotics at that time,” Barouch said.

“Although it can be a serious illness, it’s usually easily treatable with antibiotics as long as it’s caught early. So now it’s a very treatable disease. It shouldn’t create the fear that people had in the Middle Ages of the Black Death,” he said. “If anyone develops symptoms consistent with the plague — usually the initial symptoms are fever, chills and swollen lymph node — then seek medical attention, because at the early stages, the plague is easily treatable with antibiotics.”

There is a Yersinia pestis vaccine, but Moorjani said it is recommended only for high-risk people like scientists who work directly with the bacterium.

“Most people don’t need the vaccine,” he said.

People can take basic precautions to keep themselves and their pets healthy, Moorjani said, by maintaining good hygiene in and around the home to prevent contact with fleas and rodents. They should also leash their pets outdoors and use good flea control, he added.

When taking part in outdoor activities, people should take precautions against flea bites and avoid handling animal carcasses, according to the World Health Organization.

“Good general hygiene and some rational protection at the individual level can easily prevent” plague infections, Moorjani said.