Health officials have confirmed that an Oregon man has the plague after he was bitten while trying to take a dead rodent from the mouth of a stray cat.

The unidentified man, who is in his 50s, remained in critical condition Friday at a Bend hospital. His illness marks the fifth case of plague in Oregon since 1995.

Fleas that normally live on rodents are the source of plague bacteria for humans and animals. (Eric Risberg/Associated Press)

State public health veterinarian Dr. Emilio DeBess says the man was infected when he was bitten by the stray his family had befriended. The cat died and its body is being sent to the U.S. Centers for Disease Control and Prevention for testing.

Karen Yeargain, communicable disease coordinator for Crook County, said the sick man lives in rural area outside the Central Oregon city of Prineville.

DeBess, who is in Prineville investigating, said test results confirmed what officials had suspected, that the man had become infected with Yersinia pestis, the bacterium that devastated Europe during the Middle Ages.

DeBess has collected blood samples from two dogs and another cat that lives with the man's family. DeBess also collected blood samples from neighbors' pets and from animals in the local shelter to determine whether the area has a plague problem.

More than a dozen people who were in contact with the sick man have been notified and are receiving preventive antibiotics.

There are three types of plague:

Bubonic, which infects the lymph nodes.

Pneumonic, which infects the lungs.

Septicemic, which infects the blood.

The man's infection is septicemic, Yeargain said, which causes a "very significant generalized illness."

Symptoms of the plague in humans, which typically appear within four days, include fever, chills and a bloody or watery cough. In pets, plague typically presents itself with enlarged lymph nodes under the jaw, as well as fever and tiredness.

"The plague is something that is always around. In some areas of the country, they have very regular outbreaks in the rodent community," Yeargain said. "Humans don't tend to come in direct contact with it as much here in Oregon, so we don't think about it as much."

Plague is spread to humans or animals through a bite from an infected flea or by contact with an animal sick with the disease.

Fleas that normally live on rodents are the source of the plague bacteria. Domestic cats come into contact with these fleas, or with rodents who have been infected by the fleas, when they roam outdoors and hunt rodents.

"The reality is that, in rural areas, part of the role of cats is to keep the rodent population controlled around our homes and barns," Yeargain said.

Human cases of plague are very rare in Canada with the last case reported in 1939, according to the Public Health Agency of Canada's website.