Lyme disease is an inflammatory 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

Early localized Lyme infection; Lyme borreliosis; Stage 1 Lyme disease; Lyme disease - primary

Lyme disease is caused by the bacteria Borrelia burgdorferi (B. burgdorferi). Certain ticks carry the 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 you are bitten by an infected tick.

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

Risk factors for Lyme disease include walking in high grasses, taking place in activities that increase tick exposure, and having a pet that may carry ticks home.

Not everyone infected with the Lyme disease bacteria gets ill. Among those who do become ill, the first symptoms resemble the flu and include fever, headache, chills, muscle pain, and lethargy. This is the primary stage of the disease, also known as primary Lyme.

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 lesion can be larger than 1 to 3 inches wide.

Stiff neck, joint inflammation, body-wide itching, unusual or strange behavior, and other symptoms may be seen in persons with later stages of the disease.

Note: Deer ticks can be so small that they are almost impossible to see. Therefore, many people with Lyme disease never even saw a tick. These people are more likely to develop symptoms because the tick remained on their body longer.

A blood test can be done to check for antibodies to the bacteria that causes 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, so it is often not accurate early in the disease.

A skin biopsy can sometimes identify the Lyme disease bacteria.