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Plague detected in Lake Tahoe area

SOUTH LAKE TAHOE, CA - JULY 22: Visitors hike through DL Bliss State Park at Lake Tahoe on July 22, 2014 near South Lake Tahoe, California. Lake Tahoe is among Califonria's major tourist attractions.

Sean Gallup, Getty Images

A flea from a yellow-pine chipmunk in the South Lake Tahoe area has tested positive for plague, California health officials report.

The flea was sampled from one of three rodents trapped in the Fallen Leaf campground area during routine testing in May. State test results confirmed plague late last week. Health officials are not aware of any human contact with infected rodents in the area, and additional testing will be performed this week.

Plague is an infectious bacterial disease spread by squirrels, chipmunks, and other wild rodents -- and their fleas -- that is naturally present in many parts of California. People can become infected when they are bitten by a flea that has plague or through close contact with an infected rodent or pet.

Symptoms include fever, nausea, weakness, and swollen lymph nodes and usually show up within two weeks of initial contact with an infected animal. The disease can be treated with antibiotics, but if it's not caught early, can turn deadly.

The disease killed millions of people in Europe in the Middle Ages in a series of outbreaks known as the Black Death. However, now it is very rare, especially in the U.S.

According to the Centers for Disease Control and Prevention, in recent decades, an average of seven human plague cases are reported nationwide each year. Most human cases in the United States are scattered in rural areas in the west, including northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and far western Nevada.

Last year, a 16-year-old boy died of plague in Larimer County, Colorado. Later in the summer, the disease claimed another victim in the state, this time an adult.

There were two human cases of plague in California in 2015 after exposure to infected rodents in Yosemite Valley. Both people were treated and fully recovered.

Plague can be prevented by avoiding contact with wild rodents and by keeping pets away from rodent burrows.

Currently in California, warning signs have been posted in the affected area and visitors are advised to report any dead or sick rodents.

Health officials offer the following tips to help people protect themselves:

  • Do not feed squirrels, chipmunks or other wild rodents.
  • Never touch sick, injured or dead rodents.
  • Do not camp, sleep or rest near animal burrows or areas where dead rodents are observed.
  • Look for and heed posted warning signs.
  • Wear long pants tucked into boot tops and spray insect repellent containing DEET on socks and pant cuffs to reduce exposure to fleas.
  • Leave pets home if possible; otherwise keep pets on a leash. Do not allow pets to approach sick or dead rodents or explore rodent burrows. Protect pets with flea control products.
  • Pet cats are highly susceptible to plague and can pose a direct threat to humans. Keep cats away from rodents. Consult a veterinarian if your cat becomes sick after being in contact with rodents.

If you get sick after being in an area where plague is known to occur, contact your physician immediately and tell the doctor that you may have been exposed to plague.

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    Ashley Welch covers health and wellness for CBSNews.com