Bubonic Plague is Back in the U.S.

A man from South Lake Tahoe, was confirmed to have contracted the plague earlier this week, California’s first case of plague in five years, according to the El Dorado County health department. In July, Colorado also saw its first case in five years when a southwestern region resident, who has since recovered, was infected, according to the Colorado Department of Public Health and Environment. Navajo County public health officials documented a case in Arizona late July. And two cases this year were reported in New Mexico, including a man who died.

“Bubonic plague in the U.S. is not the same scenario as the historical Black Death, and we do not need to be afraid of it in the same way,” Susan Jones, a professor of ecology, evolution and behavior at the University of Minnesota College of Biological Sciences, said.  Though tragic, the cases this year aren’t unusual, she said.  The U.S. averages seven human cases of plague each year, according to the Centers for Disease Control and Prevention. In 2006, cases reached a high of 17.  There had not been a plague fatality in the U.S. since 2015, which had 16 total cases, four of which resulted in deaths, according to the CDC. 

Though there is limited information surrounding the death of the man in Rio Arriba County on the New Mexico-Colorado border, the New Mexico Department of Health reported the case as septicemic plague, rather than the much more common bubonic plague.  Both septicemic plague and bubonic plague are caused by the same bacteria; the name refers to what part of the body is affected, according to the Mayo Clinic. Bubonic plague occurs when the infection causes large, swollen lymph nodes, called buboes. Septicemic plague refers to an infection in the blood, and can be the first sign of infection or develop from untreated bubonic plague, according to the CDC. Neither are contagious.  Only the third form of plague — pneumonic plague — can be spread from person to person. Pneumonic plague occurs when the infection gets into the lungs, either from untreated bubonic or septicemic plague, or from inhaling infected droplets from another person. It is the most serious form of the disease, the CDC says.

The majority of cases occur in the Four Corners area, where Arizona, Colorado, New Mexico and Utah meet, though plague is detected in rodents across the West. According to Jones, this is due to the squirrels and prairie dogs that live in these areas and harbor plague-carrying fleas. These fleas can make their way to humans by latching onto pets that roam in rural areas.