Plague is a bacterial disease people can get if they are bitten by an infected rodent flea. Most persons with plague develop fever and swollen lymph nodes. Plague is treatable with antibiotics, but can progress to severe and sometimes fatal illness if diagnosis and treatment are delayed. Squirrels, chipmunks, and other rodents in many areas of California can carry plague. Persons visiting, hiking, or camping in these areas should avoid contact with rodents.