Deschutes County Health Services said they believe the man who developed symptoms contracted the case from his pet cat. 

People are most often exposed to plague through the bites of fleas that carry the disease-causing "Yersinia pestis" bacteria. Domestic pets can also become infected if they hunt plague-infected rodents or are bitten by a similarly infected flea.

Pets can then transmit the infection to humans through tissue or bodily fluids such as respiratory droplets from coughing. Alternatively, they can also carry fleas that have bitten humans into the home. Cats are particularly susceptible to plague because their bodies have difficulty clearing the infection and they are more likely to chase and catch rodents than other pets.

While plague is much rarer in dogs, four cases of plague were reported in Colorado in 2014 among people who had close contact with an infected pit bull terrier, including the dog's owner and two veterinary clinic workers. 

Deschutes County health officer Dr. Richard Fawcett said the cat involved in the latest case was "very sick" and had a draining abscess, indicating a fairly significant infection.

Fawcett said the owner's infection probably started in a lymph node known as "bubonic plague". By the time the owner was hospitalized, the infection was said to have progressed into the bloodstream.The patient "responded very well to antibiotic treatment," Fawcett added.  

Fawcett said doctors were also carefully administering antibiotics to the patient's close contacts to prevent potential infections from developing into symptoms.

Oregon's last human plague case was in 2015. At the time, the state health department said a young girl was likely infected from a flea bite during a hunting trip.