A person in Wyoming has fallen sick with a rare but serious case of pneumonic plague, reportedly catching the infection from a pet cat.
The Wyoming Department of Health (WDH) announced on September 15 that the patient with pneumonic plague “had contact with sick pet cats.” Cat owners need not panic, however. While plague has a nasty reputation (the deadliest pandemic in recorded history isn’t great for PR), the risk of plague in the US is low, with between 1 to 17 cases each year, according to the CDC.
The bacteria that cause plague (Yersinia pestis) has a lifecycle involving rodents and their fleas, both acting as long-term reservoirs for the bacteria. Occasionally, the rodents or fleas will transmit the bacteria to another species. This patient’s adventurous cat may have come into contact with an infected rodent while rooting around outside, then came into close contact with the owner, infecting them with the bacteria.
Plague can also be transmitted from person to person through close contact with someone who has pneumonic plague, so the WDH is notifying individuals who have made contact with the infected patient and may require a pre-emptive dose of antibiotics.
Yersinia pestis is best known as the pathogen that caused the Black Death in the form of bubonic plague. This was the most fatal pandemic recorded in human history, responsible for the death of 75 to 200 million people. However, researchers have found evidence of the bacteria in hunter-gatherers who died over 5,000-years-ago.
Plague was first introduced into the US in the early 20th century via rat-ridden ships. Most cases of the plague in the US have tended to be isolated to the western side of the country, primarily Northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and far western Nevada.
However, most recent cases in the US have been bubonic plague, not pneumonic plague. The disease comes in three forms: bubonic, pneumonic, and septicaemic. Bubonic is the most common form of the disease, most often transmitted to humans from a flea bite. Along with a fever, headache, chills, and weakness, it can also lead to one or more painfully swollen lymph nodes called buboes. Left untreated, it can spread to other parts of the body.
Pneumonic plague is considered more contagious. It is spread person-to-person through droplets in the air, or if untreated bubonic or septicemic plague spreads to the lungs. This form causes symptoms including fever, headache, and weakness. It also causes rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody mucous. All forms of the disease can prove deadly, although it can be treated with antibiotics if caught early.
Dr Alexia Harrist, state health officer and state epidemiologist with WDH, explained the risk of contracting plague in Wyoming is very low. That said, the disease has been documented throughout the state in domestic and wild animals before, so it's wise to stay cautious if you're going near known rodent habitats.
“It’s safe to assume that the risk for plague exists all around our state,” Dr Harrist said in a statement. “While the disease is rare in humans, it is important for people to take precautions to reduce exposure and to seek prompt medical care if symptoms consistent with plague develop.”