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