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Lyme Disease

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What is Lyme disease?

Lyme disease is an infection caused by the bacterium Borrelia burgdorferi, which is carried primarily by the deer tick and the black legged tick. People bitten by an infected tick may develop an inflammatory condition, which first affects the skin and then may spread to the joints, nervous system, and other body systems.

The ticks that cause Lyme disease are tiny, about the size of the head of a pin or a speck of dirt. They can be found anywhere on the body but tend to attach themselves to areas such as the scalp and groin. People who have exposure to ticks but have not been bitten will not be infected by Borrelia burgdorferi (B. burgdorferi), and many who are bitten will not develop Lyme disease. This is because not every tick is infected and because it can take the tick from 24 to 72 hours after attachment to transmit the bacterium.

Lyme disease is found throughout the northern hemisphere, but the strains of bacteria that cause it and the insects that carry it vary from region to region. In the United States, Lyme disease occurs most frequently in northeastern and west coast states. The vast majority of the cases occur in the spring and summer when people spend more time outside and the ticks are active.

According to statistics available from the Centers for Disease Control and Prevention (CDC), 22,014 confirmed cases of Lyme disease were reported in the U.S. in 2012. In that same year, 95% of Lyme disease cases were reported from 13 states (see map on this CDC web page). 

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