Campgrounds in a forest outside Los Angeles have closed down after lab tests confirmed presence of plague in a squirrel. Health Authorities said that the section of the forest will be closed for at least a week.

The entry restriction applies to the recreational centers- Broken Blade, Twisted Arrow, and Pima Loops of the Table Mountain Campgrounds in the Angeles National Forest, which encompasses some 655,000 acres in the San Gabriel Mountains.

Plague is a severe and deadly infection caused by the bacteria Yersinia pestis. People can get infected with plague by exposure to disease-carrying rodents such as rats. Bubonic plague or "Black Death" killed 25 million people in Europe during the Middle Ages. The disease still infects many people in Asia and Africa. It's presence in the U.S. is rare and is limited to certain regions such as parts of California, Arizona, Colorado, and New Mexico.

Los Angeles County Department of Public Health and U.S. Forestry Service officials said that they have notified the campers in the region about the spread. The health department will spray the squirrel burrows to kill all fleas and will conducted further tests on the squirrels before opening the campgrounds for the public.

"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," said Jonathan E. Fielding, M.D., M.P.H., Director of Public Health and Health Officer in a Health Advisory. "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."

Common symptoms of bubonic plague include enlargement of lymph glands along with fever and chills. Many people respond well to antibiotics during early stages of infection.

Health Officials said that visitors must not feed the rodents or leave any food at camp sites. Also, pets must be given vaccines before entering the camps.

"Protection with an insect repellant containing DEET is also recommended for persons visiting the Angeles National Forest and engaging in outside recreational activities in other areas of LA County," said Dr. Fielding. "Insect repellant can help protect people against fleas, mosquitoes, and ticks. Products containing DEET are not safe for use on pets."