My WebMD Sign In, Sign Up

Ask Your Question

WebMD Answers

120 Characters remaining
120 Characters remaining
  • First, try and keep your question as short as possible.
  • Include specific words that will help us identify questions that may already have your answer.
  • If you don't find your answer, you can post your question to WebMD Experts and Contributors.


Posted: | Report This Report Question |

Answers From Experts & Organizations (1)

Medical Reference

Lyme disease is caused by infection with Borrelia burgdorferi (B. burgdorferi) bacteria.

How the disease is spread

Lyme disease is spread when you are bitten by a tick that is infected with B. burgdorferi bacteria. When an infected tick bites you, bacteria travel to the tick's salivary glands and then into your body through your skin. It takes about 24 hours for a tick to attach itself to the skin and begin to feed. The tick generally must be attached to you for about 36 hours in order for it to transmit the Lyme disease bacteria.

In the United States, the two types of ticks that carry Lyme disease bacteria are:

  • Deer ticks, which spread Lyme disease in the northeastern and upper Midwestern U.S.
  • Western black-legged ticks, which spread Lyme disease along the Pacific coast-mostly northern California and Oregon.

Dogs, cats, and horses can become infected with Lyme disease bacteria, but they cannot pass the illness to humans. But infected ticks may fall off the animals and then bite and infect humans. Animals may develop symptoms similar to those seen in people, including fever and swollen joints. A vaccine for dogs is available in some states.

There is no convincing evidence that Lyme disease can be spread to humans by insects such as mosquitoes, flies, or fleas.

Is Lyme disease contagious?

Lyme disease is not contagious and cannot be spread from person to person. But certain precautions should be taken to prevent spread of the illness through ways such as blood transfusions.

  • People with active Lyme disease should not donate blood, because the bacteria that cause the illness can be transmitted this way. People who were previously treated for Lyme disease may be able to donate blood, but they should check with the blood bank first.
  • A pregnant woman may be able to pass Lyme disease to her unborn child, but proven cases are rare. Lyme disease has not been shown to cause birth defects or fetal death.
  • There is no evidence that breast-feeding mothers can pass the illness to their babies through breast milk. But a nursing mother who is suspected of having Lyme disease may be asked to stop nursing until she has completed a course of antibiotic therapy. The baby is also watched closely for symptoms of Lyme disease.

This answer should not be considered medical advice...down arrowThis answer should not be considered medical advice and should not take the place of a doctor’s visit. Please see the bottom of the page for more information or visit our Terms and Conditions.up arrow

| Report This Report Answer

Was this helpful?


Thanks for your feedback.

35 of 43 found this helpful
Read the Original Article: Lyme Disease Causes and Transmission
WebMD Medical Reference from Healthwise Healthwise This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information. © 1995-2011 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.