The CDC is urging doctors to consider a diagnosis of the plague if a patient presents with fever, abdominal pain, and nausea and vomiting, especially if the individual has recently visited the Western United States or are residents of the region.
Since April, 11 people have been diagnosed with the human plague – an unusually high number, considering between 2001 and 2012, the annual number of cases of the disease reported in the U.S. ranged from one to 17, the CDC said in a statement. The median number of annual plague cases across the past decade had been three. 
“It is unclear why the number of cases in 2015 is higher than usual,” the agency said.
People can get the plague if they are bitten by an infected flea, or by coming in close contact with another infected person or animal, including cats and dogs. The disease, which is caused by the bacterium Yersinia pestis, is rare but can be deadly.
The majority of the cases this year have occurred in the western U.S., with four cases in Colorado and two each in Arizona, California, and New Mexico, as well as Oregon. One of the individuals infected in California is a resident of Georgia. Both of the California cases have been linked to exposures at or near Yosemite National Park. Three of the patients – aged 16, 52 and 79 – have died. Nine of the 11 cases have been males.
In addition to urging doctors to consider the plague as a potential cause of symptoms, the CDC is also telling the public to wear long pants when possible, and use insect repellent on clothing and skin. The agency is also saying people should avoid direct contact with sick or dead animals, and avoid feeding squirrels, chipmunks or other rodents.
Bubonic plague accounts for approximately 80 percent of plague cases. Also known as the Black Death, the bubonic plague killed 50 million people in Europe during the 14th century. The disease used to be deadly in 93 percent of cases, but thanks to antibiotics, the death rate has dropped to about 16 percent.
Several U.S. campgrounds have been temporarily closed to allow for them to be fumigated after dead, plague-infested squirrels were found on the grounds.
 Yahoo News