What is Lyme disease?

Lyme disease is a bacterial disease caused by Borrelia burgdorferi, a spiral-shaped bacterium. The disease was first recognized in 1975 after researchers investigated why unusually large numbers of children were being diagnosed with juvenile rheumatoid arthritis in Lyme, Connecticut and two neighboring towns. Further investigations showed that tiny deer ticks infected with the bacterium were responsible for the outbreak of arthritis. Ordinary "wood ticks" and "dog ticks" do not carry the infection.

What are the symptoms of Lyme disease?

In most people, the first symptom of Lyme disease is a red rash known as erythema migrans. The rash starts as a small red spot that expands over a period of days or weeks, forming a circular, triangular, or oval-shaped rash. Because it appears as a red ring that surrounds a clear center area, the rash may resemble a bull's eye.

The rash can range in size from that of a dime to the entire width of a person's back. It appears within 1 to 4 weeks of the tick bite, usually at the site of a bite. As infection spreads, several rashes can appear at different sites on the body.

The rash may be accompanied by symptoms such as fever, headache, stiff neck, body aches, and fatigue, which can last from a few days to a few weeks.

If the infection goes untreated, a majority of those affected may develop repeated attacks of painful and swollen joints that last a few days to a few months.

Lyme disease can also affect the nervous system, causing symptoms such as:

  • Stiff neck and severe headache (meningitis).
  • Temporary paralysis of facial muscles (Bell's palsy).
  • Numbness, pain, or weakness in the limbs, or poor motor coordination.

Memory loss, difficulty with concentration, and a change in mood or sleeping habits have also been associated with Lyme disease. However, Lyme disease rarely causes these nonspecific symptoms on an ongoing basis.

Less commonly, Lyme disease can result in eye inflammation, hepatitis, and severe fatigue, although none of these problems is likely to appear without other Lyme disease symptoms being present.