A Colorado man diagnosed with pneumonic plague, a rare form of the disease that is also the most life-threatening, is the state's first confirmed human case of the illness in a decade, officials said on Wednesday.
The man was found to have the disease after the family dog died unexpectedly, and a necropsy concluded the animal was afflicted with pneumonic plague, the Colorado Department of Public Health and Environment said in a statement.
The unidentified man and his dog were believed to have contracted the disease in an eastern Colorado county. There was no word on the man's condition.
The bacteria that causes plague occurs naturally in the western United States, particularly in Colorado, New Mexico, Arizona and California, according to the U.S. Centers for Disease Control and Prevention.
The plague is transmitted by fleas to rodents, usually prairie dogs. When an infected animal dies, the disease is spread when the fleas find another host.
Pneumonic plague is the same bacteria that causes bubonic plague, but it infects a person's lungs. Symptoms include fever, headaches, shortness of breath, chest pains and a cough.
It is the most serious form of the disease, Colorado health officials said, adding that it is the only form of plague that can be transmitted person-to-person, usually through infectious droplets from coughing.
Since 1957, 60 human cases of pneumonic plague have been identified in Colorado, and nine were fatal, the health department said.
"Although human cases occur infrequently, plague is severe and potentially life-threatening if not detected and quickly treated with common antibiotics," the department said.