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Lyme disease (borreliosis) is caused by a spiral-shaped bacterium, Borrelia burgdorferi, and transmitted to humans by the black-legged tick, Ixodes scapularis. It is the most prevalent tickborne infectious disease in the United States. State health departments reported 28,921 confirmed cases and 6,277 probable cases of Lyme disease to CDC in 2008. This represents a 5% increase in confirmed cases compared to 2007.
Typically, the first symptom of Lyme disease is a red rash known as erythema migrans (EM). The telltale rash starts as a small red spot at the site of the tick bite and expands over time, forming a circular or oval-shaped rash. As infection spreads, rashes can appear at different sites on the body. Erythema migrans is often accompanied by symptoms such as fever, headache, stiff neck, body aches, and fatigue.
After several months of B. Burgdorferi infection, slightly more than half of people not treated with antibiotics develop recurrent attacks of painful and swollen joints, most commonly in the knees. About 10 to 20 percent of untreated people develop chronic arthritis.
Lyme disease can also affect the nervous system, causing such symptoms as stiff neck, Bell's palsy, and numbness in the limbs. Less commonly, untreated people can develop heart problems, hepatitis, and severe fatigue.
Healthcare providers may have difficulty diagnosing Lyme disease because many of its more common symptoms are similar to those of other disorders and viral infections. In addition, the only distinctive sign unique to Lyme disease—the EM rash is absent in at least one-fourth of the people who become infected.
The National Institutes of Health (NIH) has funded several studies on the treatment of Lyme disease. These studies have shown that most patients can be cured with a few weeks of antibiotics taken by mouth. Antibiotics commonly used for oral treatment include doxycycline, amoxicillin, or cefuroxime axetil. Patients with certain neurological or cardiac forms of illness may require intravenous treatment with drugs such as ceftriaxone or penicillin.
Patients treated with antibiotics in the early stages of the infection usually recover rapidly and completely. A few patients, particularly those diagnosed with later stages of disease, may have persistent or recurrent symptoms. The authors of studies sponsored by the National Institutes of Health have concluded that these patients may benefit from a second 4-week course of therapy and that longer courses of antibiotic treatment are not beneficial. Longer courses of antibiotics have been linked to serious complications, including death.
Studies of women infected during pregnancy have found that there are no negative effects on the fetus if the mother receives appropriate antibiotic treatment for her Lyme disease. In general, treatment for pregnant women is similar to that for non-pregnant persons, although certain antibiotics are not used because they may affect the fetus. If in doubt, discuss treatment options with your health care provider.