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  • Lyme disease should be considered in individuals who have a reasonable risk of exposure to Borrelia burgdorferi-infected ticks and who have the characteristic complex of signs and symptoms.
  • Classic clinical features occur in stages:
    • Early localized disease (3–30 days after tick bite): a single hallmark skin lesion erythema migrans (EM), occasionally associated with fever, malaise, headache, arthralgias, and myalgias; less commonly, these latter symptoms can occur in the absence of EM.
    • Early disseminated disease (weeks to months after tick bite): multiple EM lesions and associated fever, migratory arthralgias, and myalgias; acute pauciarticular arthritis; carditis manifested primarily as atrioventricular (AV) nodal block; neurologic features, including cranial nerve (especially facial nerve) palsies, lymphocytic meningitis, and radiculoneuropathies.
    • Late disease (several months to years after tick bite): primarily neurologic features, especially peripheral neuropathies and chronic mild encephalopathy; arthritis, including monoarticular and migratory pauciarticular arthritis.
  • Supporting serologic evidence of exposure to B burgdorferi is present in most cases but can be absent in early infection.

Lyme disease is a multisystem disorder caused by infection with spirochetes of the genus Borrelia burgdorferi sensu lato: B burgdorferi sensu stricto, B garinii, and B afzelii. Hard-shelled ticks of the Ixodes family, primarily I scapularis and I pacificus in the United States and I ricinus in Europe, serve as vectors for infection. In the United States, the disease first came to medical attention in 1975 in the region around Lyme, Connecticut, where a clustering of children with presumed juvenile arthritis was observed. Lyme arthritis, as it was initially termed, was soon found to be one manifestation of systemic infection with B burgdorferi. Beginning with a characteristic skin lesion, erythema migrans (EM), early infection was either confined to the skin or disseminated to other sites, with disease most commonly found in the skin, heart, joints, and nervous system. Lyme disease is not a new entity; in Europe, EM had been associated with I ricinus tick bites since the early 20th century, and the skin disease was treated successfully with penicillin after spirochetes were visualized in biopsy specimens in the mid-1900s. Other systemic manifestations were occasionally present, especially neurologic disease (Bannwarth syndrome), but the broad clinical spectrum was not fully appreciated until the late 1970s.

Since its emergence in the United States 40 years ago, Lyme disease has become the most common vector-borne infection in this country. In 2008, 28,921 confirmed and 6277 probable cases of Lyme disease were reported to the Centers for Disease Control and Prevention (CDC) (see 2008.htm for the 2008 revised case definition of Lyme disease). More than 86% of confirmed cases originated from only 9 states: New York, Massachusetts, Pennsylvania, New Jersey, Connecticut, Maryland, Wisconsin, New Hampshire, and Minnesota. Delaware, Maine, and Virginia have experienced an increase in case reporting, accounting for an additional 8% of total confirmed cases in 2008. Cases of Lyme disease have been reported from 49 states and the District of Columbia, and also occur in other areas of ...

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