A resident in California has recently tested positive for the plague, an infectious disease often referred to as the Black Death, which historically ravaged populations but now strikes only a handful of Americans annually. The unidentified individual, from the popular vacation destination of Lake Tahoe in El Dorado County, is believed to have contracted the plague after being bitten by an infected flea while camping. California health officials confirmed the person is recovering at home under medical care.

This marks El Dorado County's first confirmed case of the plague since 2020, which was also thought to have originated in the South Lake Tahoe Area. Prior to that, California had not detected a case since 2015. Nationwide, the most recent US case occurred last month in Colorado, which unfortunately proved fatal. On average, the Centers for Disease Control and Prevention (CDC) reports just seven cases of the plague in the US each year. While modern antibiotics have drastically reduced deaths, the disease remains endemic in wildlife, particularly in areas like California and New Mexico, where rodents prone to carrying the *Yersinia pestis* bacterium thrive.

The plague is caused by the bacterium *Yersinia pestis*, primarily carried by fleas and transmitted between animals such as small mammals and rodents. Humans can become infected through flea bites, handling infected animals, or, in the case of pneumonic plague, by inhaling droplets from an infected person or animal. Historically, the medieval illness was one of the most deadly in history, known for ravaging Europe between 1347 and 1351, where it wiped out an estimated 25 to 50 million people, accounting for 30 to 50 percent of the continent's population.

Symptoms of the plague typically manifest within one to eight days of infection and include a sudden onset of fever, chills, debilitating fatigue, head and body aches, weakness, vomiting, and nausea. Often, these symptoms are accompanied by the development of painful, swollen lymph nodes, known as buboes, commonly found in the groin or armpits. These buboes are characteristic of the most common form of the disease, bubonic plague.

Without treatment, the plague can have a mortality rate of 30 to 60 percent. However, if the infection progresses to the bloodstream (septicemic plague) or the lungs (pneumonic plague), it can become nearly 100 percent deadly. Septicemic plague causes bleeding under the skin, leading to dark, black spots on the skin, a symptom that contributed to the name 'Black Death'. Pneumonic plague is the most dangerous form, capable of spreading between humans via respiratory droplets. The disease kills cells by releasing deadly toxins once it enters them.

Recent plague cases have also been recorded in other states. Arizona reported its first plague death since 2007 last month, caused by pneumonic plague. Colorado and New Mexico also saw cases last year, with New Mexico's patient being the first to die from the disease since 2020, and Colorado's being the state's first death since 2007. The rarity of these cases in the US today is largely attributed to modern antibiotics and improved hygiene practices.

Given the natural presence of plague in higher-elevation areas of California, including El Dorado County, health officials emphasize the importance of precautions. Kyle Fliflet, El Dorado County acting director of public health, advised individuals to protect themselves and their pets when outdoors, particularly while walking, hiking, or camping where wild rodents are present. Recommendations include avoiding exposure to rodents, fleas, or ticks; wearing long pants tucked into boots; and using insect repellent containing DEET. Additionally, people should never feed or touch wild rodents and refrain from camping near animal burrows or areas with dead rodents. The California Department of Health reported 45 ground squirrels or chipmunks with evidence of exposure to the plague bacterium in the Lake Tahoe Basin between 2021 and 2025, underscoring the ongoing risk in the region.