Bacteria called R. rickettsii cause it, and a tick bite is usually how you get it. Most of the symptoms are flu-like -- fever, chills, headache, nausea, insomnia, and muscle aches. A rash that doesn't itch can show up on your wrists and ankles after a few days, then spread. Antibiotics treat it, and the sooner you take them, the better. If not treated, it can lead to inflammation in your lungs, heart, and brain, then kidney failure.