Lyme disease is a bacterial infection. It is passed from the bite of an infected tick. The infection is spread by deer ticks (blacklegged ticks) and western blacklegged ticks. These ticks are tiny—about the size of a poppy seed.
Lyme disease bacteria are called Borrelia burgdorferi (B. burgdorferi). A deer tick picks up the bacteria when it bites an animal that is infected with it.
The infected tick can then bite a person. From the tick bite, the bacteria can travel to the person's bloodstream. From the bloodstream, bacteria can move to different parts of the body. It may affect the skin, joints, muscles, and nerve tissue. Ticks must be attached to a person for 2 or more days to pass the infection. If the infection is passed, symptoms usually start in 1 week.
Lyme disease is most common in the northeast United States. However, it has been reported in nearly all states.
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Lyme disease charts and figures: historical data. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/lyme/stats/graphs.html. Accessed November 12, 2021.
Lyme disease. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/lyme-disease. Accessed November 11, 2021.
Last reviewed November 2021 by Medical Review Board David L. Horn, MD Last Updated: 11/12/2021