Lyme disease: An inflammatory disease that is caused by the bacterium Borrelia burgdorferi, which is transmitted to humans by the deer tick. The first sign of Lyme disease is a red, circular, expanding rash, usually radiating from the tick bite, followed by flu-like symptoms and joint pains. After the B. burgdorferi has entered the bloodstream, it can infect and inflame many different types of tissues, eventually causing many diverse symptoms. Lyme disease is medically divided into three phases: early localized disease with skin inflammation; early disseminated disease with heart and nervous system involvement, including palsies and meningitis; and late disease, featuring motor and sensory nerve damage and brain inflammation and arthritis. Within hours to weeks of the tick bite, an expanding ring of unraised redness develops, with an outer ring of brighter redness and a central area of clearing, giving it the appearance of a bull's-eye. The redness of the skin is often accompanied by generalized fatigue, muscle and joint stiffness, swollen glands, and headache. Early treatment with antibiotics is the best strategy for preventing major problems due to Lyme disease. Further prevention of Lyme disease involves avoiding areas where ticks are common, wearing protective clothing and lotion, and immediately removing any ticks from the body. Interestingly, Lyme disease only became apparent in 1975, when mothers of a group of children who lived near each other in Lyme, Connecticut, made researchers aware that their children were all diagnosed with rheumatoid arthritis. This unusual grouping of illness that appeared to be rheumatoid eventually led researchers to the identification of the bacterial cause of Lyme disease in 1982.