Lyme disease is the most common tick-borne illness in North America and Europe. Lyme disease is caused by the bacterium Borrelia burgdorferi. Deer ticks, which feed on the blood of animals and humans, can harbor the bacteria and spread it when feeding.

You’re more likely to get Lyme disease if you live or spend time in grassy and heavily wooded areas where ticks carrying the disease thrive. It’s important to take common-sense precautions in areas where Lyme disease is prevalent.

If you’re treated with appropriate antibiotics in the early stages of the disease, you’re likely to recover completely. In later stages, response to treatment may be slower, but the majority of people with Lyme disease recover completely with appropriate treatment.

The signs and symptoms of Lyme disease vary and usually affect more than one system. The skin, joints and nervous system are affected most often.

Early signs and symptoms

These signs and symptoms may occur within a month after you’ve been infected:

• Rash. A small, red bump may appear at the site of the tick bite. This small bump is normal after a tick bite and doesn’t indicate Lyme disease. However, over the next few days, the redness may expand forming a rash in a bull’s–eye pattern, with a red outer ring surrounding a clear area. The rash, called erythema migrans, is one of the hallmarks of Lyme disease. Some people develop this rash at more than one place on their bodies.
• Flu-like symptoms. Fever, chills, fatigue, body aches and a headache may accompany the rash.

Later signs and symptoms

In some people, the rash may spread to other parts of the body and, several weeks to months after you’ve been infected, you may experience:

• Joint pain. You may develop bouts of severe joint pain and swelling. Your knees are especially likely to be affected, but the pain can shift from one joint to another.
• Neurological problems. Weeks, months or even years after you were infected, you may experience inflammation of the membranes surrounding your brain (meningitis), temporary paralysis of one side of your face (Bell’s palsy), numbness or weakness in your limbs, and impaired muscle movement.

Less common signs and symptoms

Several weeks after infection, some people develop:

• Heart problems, such as an irregular heartbeat. Heart problems rarely last more than a few days or weeks.
• Eye inflammation.
• Liver inflammation (hepatitis).
• Severe fatigue.

When to see a doctor

If you’ve been bitten by a tick and experience symptoms

Only a minority of deer tick bites leads to Lyme disease. The longer the tick remains attached to your skin, the greater your risk of getting the disease. If you think you’ve been bitten and experience signs and symptoms of Lyme disease — particularly if you live in an area where Lyme disease is prevalent — contact your doctor immediately. Treatment for Lyme disease is most effective if begun early.

See your doctor even if symptoms disappear
It’s important to consult your doctor even if signs and symptoms disappear because the absence of symptoms doesn’t mean the disease is gone. Left untreated, Lyme disease can spread to other parts of your body from several months to years after infection — causing arthritis and nervous system problems. Ticks also can transmit other illnesses, such as babesiosis and Colorado tick fever.

In the United States, Lyme disease is caused by the bacterium Borrelia burgdorferi, which is carried primarily by deer ticks. The ticks are brown and when young, they’re often no bigger than the head of a pin, which can make them nearly impossible to spot.

To contract Lyme disease, an infected deer tick must bite you. The bacteria enter your skin through the bite and eventually make their way into your bloodstream. In most cases, to transmit Lyme disease, a deer tick must be attached for 36 to 48 hours. If you find an attached tick that looks swollen, it may have fed long enough to transmit bacteria. Removing the tick as soon as possible may prevent infection.