California reports first human plague case in 5 years

Emerald bay in Lake Tahoe, California.
(Image credit: Shutterstock)

A California resident has tested positive for plague, marking the state's first human case of the disease in five years, according to health officials.

The case was confirmed on Monday (Aug. 17) in a resident of South Lake Tahoe, according to a statement from the El Dorado County Department of Health and Human Services.

The individual is described as an "avid walker" who may have been bitten by an infected flea while walking their dog in the Tahoe Keys area or along the "Truckee River Corridor" north of Highway 50, the statement said.

"Plague is naturally present in many parts of California, including higher elevation areas of El Dorado County," Dr. Nancy Williams, the El Dorado County public health officer, said in the statement. "It's important that individuals take precautions for themselves and their pets when outdoors, especially while walking, hiking and/or camping in areas where wild rodents are present. Human cases of plague are extremely rare but can be very serious." 

The patient is currently recovering at home under the care of medical professionals, the statement said.

Related: Pictures of a Killer: A Plague Gallery

The plague is caused by bacteria called Yersinia pestis, and the disease is perhaps best known for causing the Black Death in Europe in the 1300s. The infection still occurs today, although it is relatively rare and usually treatable with common antibiotics. In the U.S., about seven cases of plague occur each year, on average, according to the Centers for Disease Control and Prevention (CDC).

Humans can catch the plague through flea bites or through contact with the tissue or bodily fluids of an infected animal, the CDC says.

The last known cases of plague in California occurred in 2015 in two visitors to Yosemite National Park, the statement said. A number of factors may play a role in when and where cases of plague pop up, including the behavior of people or rodents, as well as weather patterns since warmer temperatures are favorable for flea activity, Live Science previously reported

The most common type of plague in the U.S. is known as bubonic plague, which can cause fever, nausea, weakness, and swollen and painful lymph nodes (called buboes), the CDC says. This type of plague, which is not contagious, is usually caused by a flea bite.

Steps to prevent plague infections include: avoiding contact with wild rodents (including sick, injured or dead rodents); keeping pets away from rodent burrows; keeping pets on a leash when outside; and wearing long pants and insect repellent to reduce flea exposure, the statement said.

Originally published on Live Science.  

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.