A squirrel caught in a trap at the Angeles National Forest tested positive for the bubonic plague.  The squirrel was found near campgrounds, prompting officials to shut down the campgrounds in Angeles National Forest in order to investigate the infection.  During this time, officials will be able to search for squirrel burrows and dust for fleas that transmit the plague to humans.  Public statements regarding the discovery emphasize that infection in squirrels in the area is not uncommon, but there have only been four human cases in Los Angeles County since 1984.  Moreover, human infection is rarely fatal.

According the World Health Organization, the plague is a bacterial disease that most often affects wild rodents.  Fleas normally spread it from one rodent to another and an infected flea that bites a human may also transmit the plague to the human.  This transmission is usually the bubonic form of the plague, but is rarely fatal.

In a human, the infection is characterized by a swollen lymph node draining the flea bite.  Initial symptoms of the plague develop seven to 10 days after infection.  The more dangerous form is the pneumonic plague, which occurs if the bacteria reach the lungs.  The infection is airborne, spread between individuals by coughing.  Patients can die from pneumonic plague within 24 hours after infection, but the bubonic plague is likely not fatal if treated with antibiotics early.

The Food and Drug Administration has approved an antibiotic specifically for the plague.  The antibiotic, called Levaquin, was specifically shown to improve survival rates related to plague infection.  In clinical tests, African green monkeys were infected with the bacteria related to the plague.  After being administered Levaquin, 94 percent of the infected animals survived.

News of the plague infection is likely to cause alarm because the bubonic plague, better known as the Black Death, was responsible for the deaths of as many as 25 million Europeans during the Middle Ages.  Fortunately, science and living conditions have improved since then, making it easier to prevent infection and, if infected, prevent death.

Since 1990, there have been about 1,000 confirmed cases of the plague in the U.S. and over 80 percent have been the bubonic form.  Worldwide, there are 1,000 to 2,000 reported cases annually, with epidemics occurring in Africa, Asia, and South America.  In the last 20 years, the majority of cases have come out of Africa, but the worldwide mortality rate is estimated to be 10 percent or less.  The death rate is likely to be higher in areas where the plague is more common and in developing countries where cases may remain unreported.  The last urban epidemic in the U.S. occurred in the 1920s in Los Angeles.