Elizabeth Weise, USA TODAY
The discovery of one plague-infected squirrel in Southern California is not the beginning of the Zombie Apocalypse. It's merely an indication that our public health system is working smoothly.
There are about seven cases of the plague each year in the United States, according to the Centers for Disease Control and Prevention. Most are in the West, where the Yersinia pestis bacteria that causes plague lives in rats, squirrels and other rodents and the fleas that infest them.
While the Black Death may have wiped out one-third of Europe's population in the 1300s, it couldn't happen today. Antibiotics are a very effective treatment. Today about 90% of plague victims who get prompt medical attention survive.
The discovery of the infected squirrel was routine and part of on-going public health surveillance, says Ken Gage, chief of CDC's flea born diseases section in Fort Collins, Colo. States where plague is known to exist "are quite good at responding quickly," Gage said.
In the United States plague is regularly found in the West. Since 1970, cases have been reported in Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Texas, Utah and Washington. States where the plague exists began testing rodents for the disease the 1930s and today have effective programs in place to control it, Gage said.
The plague-infected squirrel in Wrightwood, Calif., was found July 16 by the California Plague Surveillance and Control Program. As soon as tests for plague came back on Wednesday health officials closed three nearby campgrounds in the Angeles National Forest to protect camps against infection. They also posted notices in the area to warn residents to avoid dead animals that might carry fleas, Gage said.
Health officials will now track down the squirrel's burrows and dust them for the fleas that actually carry the plague bacteria. The campgrounds will be reopened after testing shows they're plague-free.
The only way to get plague is to be exposed to infected fleas or rodents or to have the plague bacteria get into an open wound or cut, the CDC says. With modern housing and pest control, that's a lot less common than it was in 1350 when entire villages died from the disease.
About 80% of plague cases in the United States occur when people come into contact with infected fleas jumping from dead animals or animal burrows to humans, Gage said.
Last summer, a 7-year-old girl was camping with her family in Colorado and got the plague from a dead squirrel. The animal-loving girl asked her parents if she could bury the squirrel. Her mother said no but the child hid the squirrel in her sweatshirt anyway. Doctors found insect bites on her torso and think fleas on the carcass bit her. After weeks in the hospital she survived.
Another 15% to 20% of cases are in hunters or trappers. "That could be hunters who have shot rabbits or trappers who have trapped infected bob cats," CDC's Gage said. In one case several years ago, a National Park Service wildlife biologist died from the plague after handling a mountain lion. He had fitted it with a radio collar. When the animal later died, the biologist found the carcass and took it back to skin it, Gage said.
A tiny proportion of cases come when people are in contact with infected cougars, bobcats and domestic cats. "Felines are very susceptible to plague and they can spread the disease to people through coughing and bites," Gage said. However there have only been 30 such cases since 1977, he said.
The plague first arrived in the United States around 1900, in rat-infested steamships arriving from infected areas, most likely Asia. There were several plague outbreaks across the west early in the century. The last major one was in Los Angeles in 1924 and 1925.
Plague symptoms include: Fever, chills, headache, weakness. and swollen and tender glands in the neck, underarms or groin.