Dr. Jonathan Edlow is the author of the new book Bull's Eye: Unraveling the Medical Mystery of Lyme Disease. In the book he chronicles the emergence of the disease, how scattered clues led to the cause — bacterium Borelia burgdorferi, and then to the deer tick that spread it. The search for the cause began in the late 1970s when people around Lyme, Conn., began suffering from unexplained arthritis, swelling, circular rashes, fatigue and other symptoms.