A ground squirrel tested positive for the deadly disease on Monday, prompting the closure of three sites in the Table Mountain Campground area: Broken Blade, Twisted Arrow and Pima Loops.
The plague is carried by infected fleas. The disease can be transmitted to humans and animals through a flea bite. But the Los Angeles County Department of Public Health officials say cases of plague in humans are rare and treatable.
"When it does occur the form that is most common is where you have an increase in the size of the lymph nodes, you have chills, you have fever and that's called bubonic plague," said Dr. Jonathan Fielding, director of the L.A. County Department of Public Health.
The three campsites will remain closed for several days while squirrel burrows are dusted to control the flea population.
In the meantime, visitors are being asked to take extra precaution while out in the forest. Authorities say campers should avoid areas with a lot of ground squirrels, and they should also avoid leaving food out for the animals. Officials also recommend visitors use insect repellent with DEET.
Since 1984, there have been only four cases of the bubonic plague, all of them non-fatal, according to health officials.