Increased plague activity in El Dorado County has prompted health officials to warn residents to stay away from chipmunks and squirrels.
Plague is an infectious disease that affects rodents and humans. Introduced into this country in 1900 when it hitchhiked to the United States on rat-infested ships, plague is caused by the Yersinia pestis bacteria.
There were 999 confirmed or probable plague cases in the United States from 1900 to 2010, according to the Centers for Disease Control. Most of the cases have been in the New Mexico, Arizona and Colorado area and in Nevada, Oregon and California.
"Plague is naturally present in many parts of California, including higher elevation of El Dorado County, so we all need to be cautious around animals that can carry it," said Dr. Alicia Paris-Pombo, the county's public health officer.
The California Department of Health routinely monitors the rodent population in the state for signs of the plague. Last September and October, three chipmunks tested positive for plague in the South Lake Tahoe area.
Two of the infected chipmunks were found near the U.S. Forest Service Taylor Creek Visitor Center and a third near the Tallac Historic Site. No human illness was reported due to the infected chipmunks.
Warning signs were posted that asked the public to report dead or sick rodents. The signs will continue to be posted this year.
The CDC's website notes that people usually acquire plague when they are bitten by a flea that is infected with the plague bacteria. Humans can also become infected from direct contact with infected tissues or fluids while handling an animal that is sick or dead from plague.
Human cases of plague are rare. The disease can be effectively treated with antibiotics.
Symptoms of plague usually show up within two weeks of exposure to an infected animal or flea, according to the county health officials
With Bubonic plague, people develop fever, headache, chills, and weakness -- and swollen, tender and painful lymph nodes, according to the CDC.
Civilization has suffered major plague pandemics through history. During the "Black Death," originating in China in 1334, it is estimated that plague killed 60 percent of Europe's population, according to the CDC.
El Dorado County Health Department tips to avoiding the plague:
Do not feed squirrels or chipmunks.
Never touch sick, injured or dead rodents.
Do not camp, sleep or rest near animal burrows.
Look for and heed plague warning signs.
Leave pets home if possible. Otherwise, keep pets confined or on a leash and away from dead rodents and rodent burrows.
Wear long pants tucked into boot tops to reduce exposure to fleas. Apply insect repellent containing DEET on socks and trouser cuffs.
If you become sick after having been in an area where plague is known to occur, consult a physician.
Call The Bee's Bill Lindelof, (916) 321-1079. Follow him on Twitter @Lindelofnews.