Chipmunks Test Positive for the Bubonic Plague in Several South Lake Tahoe Locations

Officials closed some recreational sites while the areas undergo eradication efforts

A lodgepole chipmunk sitting under a vine of leaves.
Rodents within the area undergo regular tests where officials trap them, anesthetize them, and comb them for fleas. Marshal Hedin via Wikicommons under CC BY 2.0

United States Forest Service officials closed parts of California’s South Lake Tahoe after chipmunks tested positive for the bubonic plague, reports the Tahoe Daily Tribune staff.

The closures included some of the area’s most popular and picturesque hiking trails. The trails feature grassy meadows with patches of wildflowers that meander to Lake Tahoe’s scenic shore, the Guardian’s Erin McCormick reports.

Lake Tahoe is located in the Sierra Nevada Mountains and spans the border between California and Nevada. Popular recreation sites, including the Taylor Creek Visitor Center and Kiva Beach, as well as parking areas are temporarily closed until August 6 while vector control treats the sites, according to a Facebook post from U.S. Forest Service officials at the Lake Tahoe Basin Management Unit. The small rodents had no known contact with humans thus far, per the Daily Tribune.

The bubonic plague (Yersinia pestis) is a bacterial infection that spreads through wild rodents like squirrels, rats, and chipmunks via infected fleas. Humans can contract the disease through close contact with an infected rodent or from the animal's bodily fluids as well as directly through a bite from an infected flea, reports the Daily Tribune. While the bubonic plague is best known for devastating Europe in the 1300s, the bacterial infection is now easily treatable with antibiotics, reports Rachael Rettner for Live Science.

Lake Tahoe wildlife officials regularly trap, anesthetize and comb rodents in search of fleas. If fleas are found on an animal, they are tested for plague-causing bacteria. When Yersinia pestis is detected, vector control workers treat the affected areas with an insecticide, the Guardian reports.

The plague is not uncommon in the rural areas throughout the western United States. When human plague cases occur, they typically happen in states such as Colorado, Oregon, and California, reports the Independent’s Clara Hill. The bacterium occurs naturally in some parts of California, including El Dorado County, where South Lake Tahoe is located, reports Live Science. The Centers for Disease Control and Prevention (CDC) state seven cases occur per year in the U.S. on average.

“Bubonic plague is naturally occurring in the Sierra Nevada Mountains and this region. It’s something that visitors need to take precautions about, but it’s not something that they need to worry about,” says Lisa Herron, a spokesperson for the Lake Tahoe Basin Management Unit, to the Guardian.

Human cases of plague infections are rare. Last year, a person who contracted the plague in South Lake Tahoe was the case in five years, the Daily Tribune reports. State and local officials plan on testing more rodents in the area to assess further plague risks, Live Science reports.