Lyme Disease


What Is It?

Lyme disease is an infection caused by bacteria called Borrelia burgdorferi. These bacteria are transmitted through the bites of ticks, primarily the deer tick. Not everyone who develops symptoms of Lyme disease remembers getting bitten by a tick because the deer tick is very small and its bite can go unnoticed.

Lyme disease is most common in the northeastern and midwestern United States. In fact, more than 90 percent of cases have been reported in nine states: Connecticut, Maryland, Massachusetts, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island and Wisconsin. Even within states, there are regions of high risk and others with very low rates of disease. This variation relates to where ticks that carry the bacteria live, breed and come into contact with humans.

Lyme disease infection recently has caused a great deal of public concern and confusion. Lyme disease is not the “great imitator” of other diseases, and it usually is not responsible for causing chronic fatigue syndrome or other poorly defined problems. Lyme disease is a distinct illness that causes its own very specific signs and symptoms and can be readily diagnosed. Unexplained medical conditions should not be attributed to Lyme disease simply because no other diagnosis seems likely.


After the tick bite, the first symptom is a rash called erythema migrans (EM), which is usually a flat, reddish rash that spreads from the site of the tick bite. The EM rash usually is larger than 2 inches wide and can grow larger. It often develops a central clear area known as a “bull’s eye.” The rash usually doesn’t itch or hurt. Other symptoms at this stage can include fever, muscle and joint aches, fatigue, headache and a severe stiff neck. In some cases, there are two or more of these well-defined rashes.

Over several days to weeks after the tick bite, Lyme disease can cause neurological problems, including meningitis, an infection of the lining of the brain and spinal cord; and Bell’s palsy, a weakness in facial muscles caused by nerve injury. Lyme disease also can cause carditis, an inflammation of the heart muscle that can cause irregular heart rhythms with fainting or dizziness. Months to years after Lyme disease affects the heart, changes can be seen on an electrocardiogram (EKG) even when there are no symptoms. Lyme disease also can cause arthritis, either a chronic arthritis that commonly affects one knee or episodes of intermittent swelling in several joints, called migratory arthritis.

In later stages of Lyme disease, patients can experience problems with memory and concentration.


Your doctor will ask about your symptoms and perform a complete physical and neurological examination. If you have had a recent tick bite and have managed to save the tick, your doctor may want to inspect the insect and send it to a laboratory to identify the species. Some laboratories can analyze the tick to see if it is carrying the Lyme bacteria.

Your doctor will diagnose Lyme disease based on your symptoms and the examination. Blood tests are frequently negative in the first four to six weeks of Lyme disease. The basic Lyme test is called an ELISA (enzyme-linked immunosorbent assay). However, this test often gives a false-positive result, that is, a positive result in someone who does not have the illness. Therefore, every positive or uncertain Lyme ELISA result needs to be confirmed with a test called a Western blot, which looks for more specific evidence of Lyme disease infection.

A positive Lyme blood test, even including a Western blot, does not mean that there is active disease that requires treatment. This is because blood tests can remain positive for years, even after Lyme disease has been treated or has become inactive. To aid in the diagnosis of Lyme disease (and to rule out other causes of symptoms), a sample of fluid may be withdrawn from an affected joint using a sterile needle. Cerebrospinal fluid also may be withdrawn from around the spinal cord through a spinal tap (lumbar puncture), so that it can be tested for the presence of Lyme disease antibodies and inflammation and to check for other diseases.

Expected Duration

People often recover within two to six weeks without antibiotics. Even Lyme arthritis often improves on its own as the body’s own immune system attacked the infection, although it’s common for it to return. Antibiotic therapy is highly effective at curing the illness, with significant improvement within two to six weeks after beginning antibiotic therapy.


If you are in a region where Lyme disease is more common, you can prevent the disease by:

  • Avoiding the woods, high brush, and grasses where ticks hide
  • Wearing long pants and long sleeves; white clothing makes is easier to spot ticks
  • Examining your skin for ticks soon after returning from wooded areas or areas with high grass or brush
  • Applying tick repellants (especially those that contain DEET) to the skin and clothing

Antibiotics are not prescribed for every tick bite, because the actual risk of acquiring Lyme disease is quite low, ranging from less than 0.1 percent in most areas to 5 percent in some areas of the Northeast and Midwest. One study published in the June 2001 New England Journal of Medicine demonstrated that for people in areas where Lyme disease rates are high, one dose of doxycycline (Doxy Caps and other brand names) can prevent disease if taken within three days of a tick bite. So for those at highest risk, early treatment may be appropriate. Some physicians also will prescribe antibiotics to pregnant women who have been bitten by a tick, but so far, there is no evidence of that Lyme disease affects the fetus.

A Lyme disease vaccine is no longer available because it was withdrawn from the market in 2002 due to poor sales.


For the early Lyme EM rash, doctors usually prescribe three weeks of antibiotics — either a tetracycline or a penicillin derivative, such as amoxicillin (Amoxil, Trimox and other brand names). In patients who have developed facial palsy, arthritis or carditis, this antibiotic treatment often is extended to four weeks. Some people with heart or neurological problems will be treated with antibiotics such as ceftriaxone (Rocephin) given intravenously (into a vein) for two to four weeks. Intravenous treatment also may be recommended if a patient with Lyme arthritis does not respond to oral antibiotics. Amoxicillin or erythromycin (E-Mycin and other brand names) may be recommended for children.

When To Call A Professional

Call your doctor if you develop a rash or flulike illness after you have been bitten by a tick or you could have been exposed to ticks. You also should call your doctor if you have facial paralysis, arthritis, or persistent dizziness or palpitations.

If your physician has prescribed oral antibiotics for Lyme disease and your symptoms do not improve within two to three weeks, you should call your doctor.


Patients with EM, the Lyme disease rash, rarely have problems after they have been treated with antibiotics. In some cases, patients become extremely tired (fatigued) after having a course of treatment for Lyme disease, but this problem does not tend to improve with additional antibiotics. The medical reason for this fatigue, called chronic Lyme disease, is uncertain. Many, and perhaps most, patients with chronic Lyme disease have no clear evidence of active infection, and intensive antibiotic treatment (for example, intravenous treatment for prolonged periods) usually is not effective in such situations.

About 10 percent of people with Lyme arthritis appear to have chronic (long-lasting) joint swelling despite taking antibiotics. Recent evidence suggests this is caused by an autoimmune effect, in which Lyme infection triggers the immune system to attack the body’s own cells. This problem seems to follow Lyme disease primarily among people of certain genetic types. These people may respond to medications that suppress the immune system (similar to those used in rheumatoid arthritis) rather than to continued antibiotics.


Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.