Lyme disease, caused by a tick-transmitted spirochete, typically begins with a unique skin lesion, erythema chronicum migrans. Of 314 patients with this skin lesion, almost half developed multiple annular secondary lesions; some patients had evanescent red blotches or circles, malar or urticarial rash, conjunctivitis, periorbital edema, or diffuse erythema. Skin manifestations were often accompanied by malaise and fatigue, headache, fever and chills, generalized achiness, and regional lymphadenopathy. In addition, patients sometimes had evidence of meningeal irritation, mild encephalopathy, migratory musculoskeletal pain, hepatitis, generalized lymphadenopathy and splenomegaly, sore throat, nonproductive cough, or testicular swelling. These signs and symptoms were typically intermittent and changing during a period of several weeks. The commonest nonspecific laboratory abnormalities were a high sedimentation rate, an elevated serum IgM level, or an increased aspartate transaminase level. Early Lyme disease can be diagnosed by its dermatologic manifestations, rapidly changing system involvement, and if necessary, by serologic testing.

In major endemic areas in the United States, Lyme disease commonly presents as erythema migrans with homogeneous or central redness and nonspecific flu-like symptoms. Clinical outcome is excellent if antibiotic therapy is administered soon after symptom onset.

Tick bites and prophylaxis. The best currently available method for preventing infection with Borrelia burgdorferi is to avoid vector tick exposure. If exposure to Ixodes scapularis or Ixodes pacificus ticks is unavoidable, measures recommended to reduce the risk of infection include using both protective clothing and tick repellents, checking the entire body for ticks daily, and promptly removing attached ticks, before transmission of B. burgdoiferi can occur (A-III [see tables 1 and 2 for recommendation categories, indicated in parentheses throughout this text]). Routine use of either antimicrobial prophylaxis (E-I) or serological tests (D-III) after a tick bite is not recommended. Some experts recommend antibiotic therapy for patients bitten by I. scapularis ticks that are estimated to have been attached for >48 h (on the basis of the degree of engorgement of the tick with blood), in conjunction with epidemiological information regarding the prevalence of tick-transmitted infection (C-III). However, accurate determinations of species of tick and degree of engorgement are not routinely possible, and data are insufficient to demonstrate efficacy of antimicrobial therapy in this setting. Persons who remove attached ticks should be monitored closely for signs and symptoms of tick-borne diseases for up to 30 days and specifically for the occurrence of a skin lesion at the site of the tick bite (which may suggest Lyme disease) or a temperature >38?C (which may suggest human granulo

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The incidence and the endemic range of Lyme disease in the United States have increased steadily since the disease was originally recognized in Lyme, Connecticut, in 1975. Because of the varied clinical manifestations of this illness and the use of unstandardized serologic testing methods, diagnosis is often uncertain and treatment outcomes are often difficult to evaluate. The antibiotic regimens that are commonly used in clinical practice have changed rapidly. They show much regional variation with little critical comparison of treatment results. The clinical diagnosis and the literature on the treatment of the various stages of Lyme disease are reviewed. The reported data are supplemented with recommendations based on 15 years of clinical experience with this illness.