A man hospitalized in Bend is likely suffering from the plague, marking the fifth case in Oregon since 1995.

The unidentified man, who is in his 50s, fell ill several days after being bitten while trying to get a mouse away from a stray cat. The man is now being treated at St. Charles Medical Center-Bend, where he was listed in critical condition on Tuesday.

"This can be a serious illness," said Emilio DeBess, Oregon's public health veterinarian. "But it is treatable with antibiotics, and it's also preventable."

The Black Death raged through Europe during the Middle Ages, killing about a third of the population. Today, the disease is rare, but the bacteria have never disappeared.

The man, who lives in rural Crook County, was bitten Saturday, June 2. He developed a fever a few days later. By Friday, June 8, he was so sick that he checked himself into St. Charles Medical Center-Redmond. He was later transferred to the larger facility in Bend.

Karen Yeargain, communicable disease coordinator with

, said lab tests are being done to confirm whether the man has the plague, but she said he is suffering from classic symptoms.

There's one bacterium that causes the disease -- Yersinia pestis -- but it can develop into three types of illnesses depending on how an individual's body reacts. Initially, the man had swollen lymph nodes -- a sign of bubonic plague -- but now he's showing signs of septicemic plague, when the bacteria multiply in the bloodstream. Symptoms include abdominal pain, bleeding mouth, nose or rectum and dying tissue. The third type is pneumonic plague, which affects the lungs.

DeBess said it's not clear whether the man was bitten by the mouse or by the cat. The feline died, and its body has been sent to the Centers for Disease Control and Prevention for testing. The cat was abandoned in the man's neighborhood about six years ago and stuck around. Yeargain said the man and his family had a lot of contact with it. He was bitten on the hand.

"Taking a mouse out of a cat's mouth is probably not a good idea," DeBess said.

Plague bacteria are carried by fleas, which typically infest rodents. People can become infected through flea bites or through contact with an infected animal. Some animals, including dogs, that have been exposed to the bacteria carry antibodies but do not get the plague and are not infectious.

DeBess said Oregon has a record of plague cases dating to 1934, with about a case a year and some periods when no cases appear. The prevalence of the disease depends in part on the weather and food supplies. When rodents flourish, so do fleas. That increases the likelihood of infection.

A total of four people in Oregon died from the plague since 1934, DeBess said.

The four people sickened in the past 17 years – one in 1995, two in 2010 and one in 2011 – have recovered.

The man is being treated with antibiotics. Other members of his family have been given a preventative dose, Yeargain said. The disease can be spread among people through bodily fluids.

A plague vaccine exists but is no longer sold in the U.S.

Everyone in Oregon who has fallen ill with the plague since 1934 has lived in a rural setting. But people in urban areas can become infected, too, health officials said.

DeBess said people should be cautious around strays and should not handle wild animals. For example, Northern California has suffered waves of squirrel deaths caused by the plague.

Health officials advise pet owners to protect their cats and dogs against fleas by giving them topical treatments or using a flea collar. The treatments are not 100 percent effective, but they do diminish the chances of pets becoming infected.

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