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Lyme borreliosis, or Lyme disease, is the most commonly reported arthropod-borne illness in both the United States and Europe.1 It was first recognized in the 1970s after epidemiologic investigations of a clustering of cases of oligoarthritis among children in eastern Connecticut established a probable microbial etiology for the disease.2 In 1981, Burgdorfer isolated a new spirochetal bacterium, Borrelia burgdorferi, from the midgut of the Ixodes dammini tick (now Ixodes scapularis).3 Recovery of the organism subsequently from cutaneous lesions, cerebrospinal fluid (CSF), and blood specimens of patients with Lyme disease in both the United States4,5 and Europe6–8 definitively linked the disease with B. burgdorferi.
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The existence of B. burgdorferi in the Northeastern United States likely predates the presence of European settlers by several thousand years.9 The incidence and range of the organism has steadily grown since its recognition in the 1970s. Deer and birds are thought to be the primary drivers in dispersal of infected ticks into new areas. In the United States, the Centers for Disease Control and Prevention (CDC) initiated surveillance for Lyme disease in 1982, and the Council of State and Territorial Epidemiologists made Lyme disease a nationally notifiable disease in 1991. Since 1992, 248,074 cases have been reported to the CDC.10 In 2006, the number of new cases in the United States was 19,931 (national median incidence 0.5 cases per 100,000 people). This represents a 101% increase in annual incidence since 1992. There is believed to be significant underreporting of Lyme disease, and the real number of new cases each year in the United States is actually thought to approach 150,000. For the 15-year period for which the CDC has data, approximately 93% of reported cases occurred in ten states located in the Northeastern, mid-Atlantic, and North Central regions: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin. Nearly all states have reported cases of Lyme disease at some point during the past 15 years, though average incidence varies markedly from 0.0 for Colorado, Montana, and Hawaii to 73.6 per 100,000 people for Connecticut. Disease in many of the states with low incidence represents travelers infected during travel to more endemic regions.
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Lyme disease is also widely distributed in Europe, with an estimated 120,000 new cases each year.11 The highest reported frequencies occur in forested areas of central and Northern Europe (Germany, Austria, Slovenia, and Sweden).12,13 The infection is also found in Eastern Russia, ...