Epidemiology of Lyme disease
المؤلف:
Mary Louise Turgeon
المصدر:
Immunology & Serology in Laboratory Medicine
الجزء والصفحة:
5th E, P249-250
2025-08-20
285
Currently, Lyme disease is a global illness. Cases have been reported on all continents except Antarctica. Since its original description more than 25 years ago, Lyme disease has become the most commonly reported (95%) vector-borne illness in the United States. This infection has emerged as a major health hazard for human beings and domestic animals. In 2011, it was the sixth most common nationally notifiable disease. It is endemic in more than 15 states in the United States and in Europe and Asia.
In some patients, Lyme disease may be transitory and of little consequence, but in others it may become chronic and severely disabling. Accurate diagnosis is therefore essential, although better laboratory techniques are still needed.
Retrospectively, the first symptom of Lyme disease apparently was recognized as early as 1908 in Sweden. In the decades that followed, the rash produced by the disease erythema chronicum migrans (ECM) was noted elsewhere in Europe, as were other symptoms that seemed to follow ECM’s eruption. Secondary symptoms, such as impairment of the nervous system, were described in France, Germany, and again in Sweden.
In the United States the European rash was almost unknown until 1969, when a case of a physician bitten by a tick while hunting in Wisconsin was reported. Although a few ECM cases were seen in Americans who had traveled to Europe, there were no further native American cases until 1975, when physicians at the U.S. Navy base in Groton, Connecticut, reported seeing four patients with a rash similar to that of ECM. At the same time, an epidemiologist at the Connecticut State Department of Health and a rheumatologist at Yale University were notified of an unusual cluster of cases of arthritis occurring in children in Lyme, Connecticut.
It was not until 1982 that Burgdorfer and Barbour isolated a previously unrecognized spirochete, now called B. burgdorferi, from I. scapularis ticks, and Lyme disease became a recognized vector-borne, infectious disease. Two factors influence the chance that a bitten patient will contract the disease, the likelihood that local ixodid ticks carry the Lyme spirochete and the likelihood of infection after a bite by an infected tick. The probability of infection after an ixodid tick bite in an area of endemic disease is about 3%, but varies in different regions from less than 1% to as high as 5%. It has been suggested that human leukocyte antigen (HLA)–DR4 (HLA-DR4) and, secondarily, HLA-DR2, may increase the risk that Lyme arthritis will become chronic and fail to respond to antibiotics.
Lyme disease does not occur nationwide and is concentrated heavily in the northeast and upper midwest. The highest number of confirmed cases of Lyme disease to date was 29,959 in 2009 (Fig. 1). Persons of all ages and both genders are equally susceptible. In 2011, 96% of Lyme disease cases were reported from 13 states (Fig.2):
• Connecticut
• Delaware
• Maine
• Maryland
• Massachusetts
• Minnesota
• New Hampshire
• New Jersey
• New York
• Pennsylvania
• Vermont •
Virginia
• Wisconsin
Fig1. Reported cases of Lyme disease—United States, 1996-2010. (Courtesy Centers for Disease Control and Prevention, Atlanta.)
Fig2. Reported cases of Lyme disease—United States, 2011. (Courtesy Centers for Disease Control and Prevention, Atlanta.)
Lyme disease is considered an emerging infectious disease because of the impact of changing environmental and socioeconomic factors, such as the transformation of farmland into suburban woodlots favorable for deer and deer ticks. Although pets may represent a spirochete reservoir, it is unlikely that humans can be infected directly by them. In areas of endemic Lyme disease, however, both adult and nymphal ticks, carried into the household by dogs and cats, may infect humans.
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