A plague-infected squirrel has closed a California campground for at least a week, according to Los Angeles County health officials.

The squirrel, trapped July 16 in the Table Mountain Campgrounds of Angeles National Forest, tested positive for the infection Tuesday, prompting a health advisory and the closing of the campground while investigators tested other squirrels and dusted the area for plague-infected fleas.

"Plague is a bacterial infection that can be transmitted to humans through the bites of infected fleas, which is why we close affected campgrounds and recreational areas as a precaution while preventive measures are taken to control the flea population," L.A. County health officer Dr. Jonathan Fielding said in a statement.

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Plague is caused by Yersinia pestis, a microscopic bug blamed for wiping out 60 percent of the European population between 1348 and 1420. It is rare nowadays, with an average of seven human cases a year in the U.S., according to the Centers for Disease Control and Prevention. It's also curable with antibiotics, but can cause serious illness or death if left untreated.

"It is important for the public to know that there have only been four cases of human plague in Los Angeles County residents since 1984, none of which were fatal," Fielding said.

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A bite from a plague-infested flea can cause fever, chills and enlarged lymph nodes, known as buboes, near the bite, according to the CDC.

"The earlier a patient seeks medical care and receives treatment that is appropriate for plague, the better their chances are of a full recovery," the agency says on its website.

L.A. County health officials are urging Angeles National Forest campers to avoid contact with wild animals, steer clear of squirrel burrows and report any dead squirrels to the department of health.

Campers should also wear DEET-containing insect repellent to ward off fleas and avoid taking pets into flea-infested areas, according to the advisory.

Click here for more information about the campground closure, or call (626) 430-5450.

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