A resident in California's popular vacation destination Lake Tahoe has tested positive for the Black Death, marking the county's first confirmed plague case since 2020. The individual, who is now recovering at home under medical care, is believed to have contracted the plague after being bitten by an infected flea while camping. This rare occurrence highlights the natural presence of plague in certain regions of California, particularly higher-elevation areas.

Plague, sometimes referred to as the Black Death, is a severe infectious disease caused by the bacterium Yersinia pestis. This bacterium is primarily carried by fleas and transmitted between animals, often rodents. Historically, the Black Death ravaged Europe between 1347 and 1351, wiping out an estimated 25 to 50 million people, representing 30 to 50 percent of the continent's population.

In the United States, plague cases are rare, with the CDC reporting an average of just seven cases annually. These cases tend to crop up most often in areas like California, New Mexico, Arizona, Utah, and Colorado, collectively known as the Four Corners region, due to a higher prevalence of rodents susceptible to Yersinia pestis. Untreated plague has a mortality rate of 30 to 60 percent; however, if it spreads to the lungs (pneumonic plague) or bloodstream (septicemic plague), it can be nearly 100 percent deadly. Modern antibiotics and improved hygiene have drastically reduced deaths, but the disease remains endemic in wildlife populations.

Symptoms of plague typically strike within one to eight days of infection and include sudden onset of fever, chills, debilitating fatigue, head and body aches, weakness, vomiting, and nausea. It is often accompanied by the development of painful swollen lymph nodes, known as buboes, in the groin or armpits, characteristic of bubonic plague, which is the most common form. If left untreated, the bacteria can enter the bloodstream and travel to the lungs, causing deadly infections. Once inside cells, the bacteria release deadly toxins.

Recent cases in the US include a fatal case in Colorado last month, and another in Arizona where an unidentified resident died from pneumonic plague, the state's first death from the disease since 2007. New Mexico also recorded a plague case last year, resulting in the patient's death, the first in that state since 2020.

Health officials, including Kyle Fliflet, El Dorado County acting director of public health, emphasize the importance of precautions for individuals and their pets when outdoors in high-risk areas. Recommendations include avoiding exposure to wild rodents or their fleas, wearing long pants tucked into boots, using insect repellent with DEET, never feeding or touching wild rodents, and refraining from camping near animal burrows or dead rodents. Studies have shown evidence of plague exposure in ground squirrels and chipmunks in the Lake Tahoe Basin, reinforcing the need for vigilance.