Lyme disease is caused by the bacteriumBorrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. Lyme disease isdiagnosed based on symptoms, physical findings (e.g., rash), and the possibility of exposure to infected ticks laboratory testing is helpful if used correctly and performed with validated methods. Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics. Steps to prevent Lyme disease include using insect repellent, removing ticks promptly, applying pesticides, and reducing tick habitat. The ticks that transmit Lyme disease can occasionally transmit other tickborne diseases as well.
Several of the patients reported having a peculiarskin rash just before developing arthritissymptoms, and many also recalled being bitten by a tick at the rash site.
Further investigations resulted in the discovery that tiny deer ticks infected with a spiral-shaped bacterium or spirochete (which was later namedBorrelia burgdorferi) were responsible for the outbreak of arthritis in Lyme. Ordinary "wood ticks" and "dog ticks" do not carry the infection. The ticks most commonly infected with B. burgdorferi usually feed and mate on deer during part of their life cycle. The recent growth of the deer population in the northeast and the building of suburban developments in rural areas where deer ticks are commonly found have probably contributed to the increasing number of people with the disease.
The number of reported cases of Lyme disease, as well as the number of geographic areas in which it is found, has been increasing. Lyme disease has been reported in nearly all states in this country, although most cases are concentrated in the coastal northeast, Mid-Atlantic States, Wisconsin, and Minnesota, and northern California. Lyme disease is also found in large areas of Asia and Europe. Recent reports suggest that it is present in South America, too.