Health A-Z

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What Is It?

Lyme disease is an infection caused by bacteria called Borrelia burgdorferi. These bacteria are transmitted through the bites of ticks, primarily the deer tick. Not everyone who develops symptoms of Lyme disease remembers getting bitten by a tick because the deer tick is very small and its bite can go unnoticed.

Lyme disease is most common in the northeastern and midwestern United States. More than 90% of cases have been reported in nine states: Connecticut, Maryland, Massachusetts, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island and Wisconsin. Even within states, there are regions of high risk and others with very low rates of disease. This variation relates to where ticks that carry the bacteria live, breed and come into contact with humans.

Lyme disease infection recently has caused a great deal of public concern and confusion. Lyme disease is usually not responsible for causing chronic fatigue syndrome or other poorly defined problems. Lyme disease is a distinct illness that causes its own very specific signs and symptoms and can be readily diagnosed. Unexplained medical conditions should not be attributed to Lyme disease simply because no other diagnosis seems likely.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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