Chipmunks Test Positive for Plague Near Lake Tahoe, Leading to Closures

You may have learned about the Black Death in history class—but as it turns out, the plague that caused the medieval pandemic is still with us and prompting occasional outbreaks of the disease centuries later.

Over the weekend, areas of South Lake Tahoe were closed to the public, after a number of chipmunks tested positive for the plague. El Dorado County spokesperson Carla Hass clarified that the chipmunks had not been in contact with any humans, according to the Tahoe Daily Tribune. The Taylor Creek Visitor Center, Kiva Beach and their respective parking lots are said to be closed through August 6.

While the incident may sound alarming, El Dorado County Public Health officials noted that "plague is naturally present in many parts of California, including higher elevations."

In August 2020, a South Lake Tahoe resident became the first person in five years to catch the plague in California, highlighting exactly how rare human cases of the plague truly are. The infected individual reportedly caught the disease after being bitten by an infected flea while walking their dog.

The Centers for Disease Control and Prevention (CDC) explains on their website that the plague is caused by the bacterium Yersinia pestis. "​​Plague occurs in rural and semi-rural areas of the western United States, primarily in semi-arid upland forests and grasslands where many types of rodent species can be involved," says the agency. "Many types of animals, such as rock squirrels, wood rats, ground squirrels, prairie dogs, chipmunks, mice, voles, and rabbits can be affected by plague."

From those populations of mammals, the plague can be spread to humans via flea bites, from "contact with contaminated fluid or tissue," or after breathing in bacteria-containing droplets from someone already infected.

Today, the plague is mainly remembered as the source of the Black Death, which spread throughout Europe over the course of the 14th century. An estimated 25 million people died from the plague—nearly a third of the continent's population at that time.

Today, the plague "is treatable with commonly available antibiotics." However, as the CDC warns, the disease is still "a very serious illness."

There are three types of plague, and each has unique symptoms. Typically resulting from the bite of an infected flea, the bubonic plague is defined by the "sudden onset of fever, headache, chills, and weakness" in addition to "one or more swollen, tender and painful lymph nodes (called buboes)."

The symptoms of septicemic plague are similar, along with "extreme weakness, abdominal pain, shock, and possibly bleeding into the skin and other organs." Additionally, the CDC reports that "skin and other tissues may turn black and die, especially on fingers, toes, and the nose."

Pneumonic plague "is the most serious form of the disease and is the only form of plague that can be spread from person to person," says the CDC. As its name suggests, it comes with symptoms of pneumonia, including "shortness of breath, chest pain, cough, and sometimes bloody or watery mucous."

It is not confirmed which type of plague had infected the South Tahoe chipmunks.

Newsweek reached out to a spokesperson from El Dorado County for further comment but did not receive a response in time for publication.