Lyme disease is an infectious disease spread through a tick bite.

Primary Lyme disease is the first stage of the disease. For specific information on the other stages or general information about Lyme disease, see:

• Lyme disease
• Stage 2 Lyme disease
• Stage 3 Lyme disease

Lyme disease is caused by the bacterium Borrelia burgdorferi (B. burgdorferi). Certain ticks may carry these bacteria. The ticks pick up the bacteria when they bite mice or deer that are infected with Lyme disease. You can get the disease if an infected tick bites you.

Risk factors for Lyme disease include:

• Having a pet that may carry ticks home
• Taking part in activities that increase tick exposure
• Walking in high grasses

The parts of the United States where the chance of getting Lyme disease is higher include:

• New England
• The mid-Atlantic states
• The north-central states

Note: Deer ticks can be so small that they are almost impossible to see. Therefore, many people with Lyme disease never knew they had a tick bite. Unlike a mosquito bite, a tick bite cannot be felt. In most cases, the tick must stay on the body for 48 hours to transmit the bacteria to humans.

The first stage of Lyme disease is considered the "primary" or early stage.

Not everyone infected with the Lyme disease bacteria gets ill. Among those who do become ill, the first symptoms resemble the flu and include:

• Chills
• Fever
• Headache
• Lethargy
• Muscle pain

There may be a "bulls-eye" rash -- a flat or slightly raised red spot at the site of the tick bite often with a clear area in the center. This spot can be larger than 1 - 3 inches wide.

A blood test can be done to check for antibodies to the bacteria that cause Lyme disease. The most common one used is the ELISA for Lyme disease test. A western blot test is done to confirm ELISA results.

The tests are usually not positive in the first few weeks after the tick bite. They are often not accurate early in the disease. Early treatment with antibiotics may prevent this test from ever being positive.

A skin biopsy can sometimes identify the Lyme disease bacteria.

Antibiotics are used to treat Lyme disease. The type of antibiotic used depends on the stage of the disease and your symptoms. The most common choices are doxycycline for older children and non-pregnant adults. Amoxicillin or cefuoxime (Ceftin) is typically prescribed for younger children.

Antibiotics are given for 10 - 21 days.

If diagnosed in the early stages, Lyme disease can be cured with antibiotics. The disease will usually get better in 3 - 4 weeks.

Without treatment, complications involving the joints, heart, and nervous system can occur.

If untreated, Lyme disease may progress to the advanced stages. Complications related to advanced Lyme disease include long-term joint inflammation (Lyme arthritis) and heart rhythm problems.

Nervous system (neurological) problems are also possible, and may include:

• Decreased concentration
• Memory disorders
• Nerve damage
• Numbness
• Pain
• Paralysis of the face muscles
• Sleep disorders
• Vision problems

Another complication is infection with bacteria that cause other tick-borne diseases, such as ehrlichiosis or babesiosis.

Call for an appointment with your health care provider if you have:

• A rash that looks like a bulls-eye
• Had a tick bite and develop weakness, numbness or tingling, or heart problems
• Symptoms of Lyme disease, especially if you may have been exposed to ticks

When walking or hiking in wooded or grassy areas:

• Spray all exposed skin and your clothing with insect repellant (spray outdoors only, do not use on face, use just enough to cover all other exposed skin, don't spray under clothing, don't apply over wounds or irritated skin, wash skin after going inside)
• Wear light-colored clothing to make it easier to spot ticks
• Wear long-sleeved shirts and long pants with the cuffs tucked into shoes or socks
• Wear high boots, preferably rubber

Check yourself and your pets frequently during and after your walk or hike.

Ticks that carry Lyme disease are so small that they are very hard to see. After returning home, remove your clothes and thoroughly inspect all skin surface areas, including your scalp.

If possible, ask someone to help you examine your body for ticks. Adults should carefully examine children.

Bratton RL, Whiteside JW, Hovan MJ, Engle RL, Edwards FD. Diagnosis and treatment of Lyme disease. Mayo Clin Proc. 2008;83:566-571.

Clark RP, Hu LT. Prevention of Lyme disease and other tick-borne infections. Infect Dis Clin North Am. 2008;22:381-396.

Wormser GP, Dattwyler RJ, Shapiro ED, Halperin JJ, Steere AC, Klempner MS, et al. The clinical assessment, treatment, and prevention of Lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2006;43:1089-1134.