Most cases occur in the Northeast, upper Midwest, and the Pacific Coast.
Mice and deer are the most commonly infected animals that serve as hosts to the tick . Most infections occur in the summer. The disease is difficult to diagnose because the symptoms mimic other diseases. Tertiary disease occurs months to years after the initial infection, and symptoms include skin, neurological, and musculoskeletal manifestations. The incidence is 8 out of 100,000 people.