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Geographic Expansion of Lyme Disease Emphasizes Importance of Recognizing Modes of Transmission

Lyme disease, although focused in the northeastern United States, has ex­panded geographically over the past few decades, with a >320% increase in the number of high-incidence counties1 and reported cases in 49 states.2 Recognition of Lyme disease has improved in endemic areas; however, health care practitioners in other areas of the United States may be unfamiliar with the clinical presentation, according to experts who participated in a Contagion® Peer Exchange panel.

The geographic spread of Lyme disease is due to multiple factors. The panelists high­lighted an increase in development leading to a greater density of deer populations and few­er small-animal predators as key contributors to the spread and transmission of the disease.

Epidemiology of Lyme Disease

Lyme disease, the most common tick-borne ill­ness in the United States and Europe, is caused by spirochetes within the Borrelia burgdorferi sensulato species complex. Approximately 95% of the confirmed cases of Lyme disease were reported from 14 states in 2015, with the highest incidence rates in Vermont, Maine, Connecticut, and Massachusetts.2

“In the early days when Lyme disease was first being described, it was found in Old Lyme, Connecticut, which is in the northeast region of the United States,” said Peter L. Salgo, MD. “And early on, everyone thought, ‘Oh, it’s a [northeastern] United States problem.’”

However, the causative organism, the spirochete Borrelia burgdorferi, trans­mitted through the bite of an infected tick, like­ly dates back several thousand years. Samuel Shor, MD, FACP, pointed out that a 5300-year-old mummy, discovered in Italy some 25 years ago, was found with evidence of knee arthritis and genetic evidence of Borrelia.

Alfred Buchwald, a Ger­man physician, was the first to describe the erythema migrans rash often seen with Lyme disease more than 130 years ago, although he did not associate the rash with a tick-borne pathogen. In the 1960s and 1970s, a group of children and adults in Lyme, Connecticut, and surrounding areas began experiencing unexplained symptoms that included arthritis, paralysis, skin rashes, headaches, and chronic fatigue. Researchers began to describe the signs and symptoms of this condition as Lyme disease, and the children reported having a tick bite before the onset of symptoms; however, the cause was still unclear. Leonard Sigal, MD, noted that many of these patients were mistakenly diagnosed with juvenile rheumatoid arthritis until researchers noticed the geographic clustering of cases.

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