What Happens

If you are bitten by a tick carrying Lyme disease bacteria, a circular skin rash often develops at the site of the tick bite within a month. The rash slowly expands and may become very large. Flu-like symptoms, such as fatigue, headache, sore muscles and joints, fever and chills, and swollen lymph nodes, also may occur. Lyme disease develops in three stages.

Early localized Lyme disease usually occurs 3 days to about a month after being bitten. If Lyme disease is not found and treated properly during the early localized stage, the infection may progress to the second or third stages of Lyme disease and involve the skin, joints, nervous system, and heart.

Early disseminated Lyme disease is the second stage. It may develop several weeks or months after you become infected and can cause:

• Skin problems, such as an expanding, circular rash at the site of the bite. More rashes can then develop on other parts of your body as the infection spreads. More serious skin problems from Lyme disease are rare in the United States but can include swelling in the earlobes and near the nipples, and severe thinning of the skin on the hands and feet.
• Joint problems, which are common and include brief episodes of pain, redness, and swelling in one or more large joints—most often the knee. Joint symptoms usually improve with antibiotic treatment.
• Early nervous system problems, such as pain and weakness in the arms and legs caused by nerve inflammation.
• Heart problems, most commonly a slow or irregular heartbeat (arrhythmia). Heart problems caused by Lyme disease are rare and are even more rare if you did not already have a weakened heart before you got Lyme disease.

Late persistent Lyme disease is the last and often the most serious stage of the disease. It may develop weeks, months, or, in rare cases, years after the initial infection and can cause:

• Joint problems, such as early arthritis that most often affects the knee. A small number of people eventually develop chronic Lyme arthritis, which usually improves with antibiotic treatment. But joints that have been badly damaged may take a long time to heal or may not respond to antibiotic treatment. In some cases, surgery to remove the lining of the affected joint (synovectomy) may be necessary.
• Late nervous system problems, such as pain, weakness, or numbness in the arms or legs that can occur when the bacterial infection has spread to the nerves or spinal cord. Severe headaches, fatigue, or problems with vision, hearing, memory, concentration, and thinking can also develop. Serious nervous system problems can cause severe headache and stiff neck due to inflammation of the tissues surrounding the brain and spinal cord (meningitis); paralysis of the nerves that control the muscles in the face; and inflammation of the brain (encephalitis). These problems sometimes go away on their own, but if they do not, they usually improve after antibiotic treatment.
• Heart problems, which are rare, but can occur months to even years after being bitten by an infected tick. The most serious heart problems—such as inflammation of the structures surrounding the heart (pericarditis)—usually resolve without any permanent damage. Unfortunately, heart problems can be the first sign of Lyme disease in a small number of people who did not have early symptoms.

Later symptoms of untreated Lyme disease, such as joint problems, weakness or numbness in the arms or legs, severe fatigue, or problems with memory and thinking, may seem like other illnesses such as fibromyalgia or multiple sclerosis.