Fear of Lyme disease may be as powerful as the disease itself. Patients may insist on being tested for infection although little evidence of it exists, and a positive result in the face of vague symptoms can add to the problem. Physicians should explain to these patients the differences in "background" seropositivity in various geographic locations and the drawbacks of instituting unnecessary treatment. Fibrositis may evolve over time after Lyme disease infection. Many factors may trigger this disorder, but some investigators propose that it is a result of musculoskeletal pain, sleep disturbance, and anxiety over the disease.