Health officials in Los Angeles have confirmed this week that a squirrel found in a National Forest in California was infected with plague.
As a precaution parts of the Angeles National Forest near Wrightwood have been closed since Wednesday.
Visitors were ordered to leave the park after the creature was trapped in a routine check. Officials have said no individuals in the area have been infected with the disease, which is known as the Black Death.
The animal - a ground squirrel - was found to be carrying the disease, which if not treated with antibiotics is usually fatal.
The plague was responsible for the deaths of an estimated 25 million Europeans during the 14th century. It is usually transmitted to humans through the bites of infected fleas.
"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," the health department chief, Dr. Jonathan Fielding, said in a statement.
According to a health advisory notice issued by the County of Los Angeles Public Health department the plague has been known to reside among the the ground squirrels in the San Gabriel Mountains.
If infected with bubonic plague symptoms in humans include enlargement of lymph glands (buboes) near the flea bite along with fast onset of fever and chills.
Previously plague-positive squirrels have been found in the area in 2010, one in 2007, two in 1996 and one in 1995.
Campers at the affected sites include the Broken Blade, Twisted Arrow, and Pima Loops areas - have been informed.