7/25/13 - A squirrel infected with plague bacteria prompted the closure of popular campgrounds in the Angeles National Forest on Wednesday, according to Los Angeles County health officials. Officials with the county and the U.S. Forest Service closed the Broken Blade, Twisted Arrow and Pima Loops areas of the Table Mountain Campgrounds near Wrightwood, a small mountain town northeast of Los Angeles. A single ground squirrel trapped July 16 was found Tuesday to have tested positive. The plague disease spreads to humans through bites from infected fleas. And though the infection had once been called the "Black Death" because it killed millions before the advent of antibiotics, infections today in the U.S. are rare and usually not fatal. "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," said Dr. Jonathan E. Fielding, the county's director of public health. More SoCal News on NBC4's FREE mobile: Details here It is not rare, however, to find plague in the ground squirrels of the San Gabriel Mountains, according to health officials. A squirrel trapped in 2010 near the Los Alamos campgrounds in Gorman carried the disease, as did one in 2007 and two in 1996 from the Stoneyvale Picnic Area near La Canada/Flintridge. Another plague-carrying squirrel was found in 1995 near a campground in Vogel Flats. Officials urged campers, hikers and picnickers in the area to avoid wild animals and particularly ground squirrels, and to make sure all people and pets are protected from fleas. Anyone who sees dead ground squirrels in recreational areas were urged to call the county Department of Public Health at 626-430-5450. Health officials recommend that visitors to the Angeles National Forest use strong insect repellents containing DEET, which can protect against fleas, mosquitoes and ticks. Products with DEET are not safe for use on pets.