Call your doctor whenever you or someone in your family develops a fever or becomes very sick (fever, severe weakness, severe headache) after:
A flea bite or any unidentified insect bite
Exposure to a sick or dead animal, even a pet cat
Travel or work in areas where rodent burrows and nests are common
Travel to the high-risk areas of the Southwestern United States or to countries where plague is most common
Also call your doctor if you develop a painful, swollen lymph node, especially if you have recently been bitten by an insect.