Bacterial infection transmitted by ticks that live on deer or mice. Marked by a bull’s-eye rash, malaise, fatigue and muscle aches, it is often misdiagnosed, although it will respond readily to antibiotics. If left untreated, it can become disabling. First noted in suburban Lyme, Connecticut, in 1975, by the early 1990s more than 10,000 cases were reported annually chiefly in the Northeast, Midwest and California. In these areas, it has challenged outdoor life patterns as people cover up and spray insecticides to avoid ticks, or abandon wooded areas altogether. Its suburban demographics may also have encouraged rapid development of a vaccine, which became available in 1997.