In the early 1970s, a mysterious clustering of arthritis occurred among children in Lyme, Connecticut, and surrounding towns. Medical researchers soon recognized the illness as a distinct disease, which they called Lyme disease. They subsequently described the clinical features of Lyme disease, established the usefulness of antibiotic therapy in its treatment, identified the deer tick as the key to its spread, and isolated the bacterium that caused it. Lyme disease is still mistaken for other diseases, and it continues to pose many other challenges: it can be difficult to diagnose because of the inadequacies of today's laboratory tests; it can be troublesome to treat in its late