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Doctors diagnose Lyme disease based on the patient's symptoms (signs of illness), history, and blood test results. There are three stages of Lyme disease: early, early disseminated, and late Lyme disease.

Symptoms—First Stage

The first stage of Lyme disease is called early Lyme disease. Early Lyme disease usually causes one or more of the following symptoms that occur days to weeks after infection:

  • Fatigue
  • Chills and fever
  • Headache
  • Muscle and joint pain
  • Swollen lymph nodes
  • Erythema migrans
Erythema migrans

Erythema migrans (see picture), the skin rash associated with Lyme disease, occurs as a circular rash that continues to grow. It may appear anywhere from 1 day to 1 month after the infected tick's bite, but it usually appears in about 7 days. The center of the rash may clear as it grows, giving it the appearance of a bull's-eye. The rash may be warm, but it is usually not painful. Sometimes, the rash includes many red patches that appear in different shapes and sizes around the body. The erythema migrans type of skin rash is different from a rash that appears as an allergic reaction to a tick or insect bite. Such reactions to a bite usually appear as a redness within hours to 1 day after a bite, do not grow, and disappear within a day or two. Erythema migrans does not occur in some patients with Lyme disease. In patients who do not get the rash, the first sign of bacterial infection can be symptoms of second- or third-stage Lyme disease.

Symptoms—Second Stage

The second stage of Lyme disease is known as early disseminated Lyme disease, which means that the infection of bacteria is beginning to spread and is affecting certain body functions. This stage occurs weeks to months after the bite of an infected tick. Problems can include:

  • Numbness and pain in arms or legs
  • Paralysis of facial muscles (usually on one side of the face)
  • Meningitis—fever, stiff neck, and severe headaches
  • Abnormal heart beat (rare)

Symptoms—Third Stage

The third stage of Lyme disease is called late (or chronic) Lyme disease. This stage can occur weeks, months, or even years after infection in patients who either never received antibiotic treatment for early Lyme disease or whose treatment did not kill all of the bacteria that cause Lyme disease. Patients with late Lyme disease may get:

  • Chronic Lyme arthritis—brief bouts of pain and swelling usually occurring in one or more of the large joints, especially the knees
  • Nervous system problems, including memory loss and difficulty concentrating
  • Chronic pain in muscles and/or unrestful sleep


From left to right: adult female, adult male, nymph, larvae (scale in cm)

A history of a known tick bite will help the doctor to know if Lyme disease caused the current symptoms. However, many people with Lyme disease do not remember being bitten by a tick. Deer ticks (picture) and western black-legged ticks are tiny and often go unnoticed. For example, nymphal deer ticks, the most common transmitters of Lyme disease, are often about 2mm, or the size of this dot ().

Blood Tests

Blood tests, also known as Lyme titers, cannot diagnose Lyme disease alone, but they are used to confirm a diagnosis. The most common blood test ordered for Lyme disease is the ELISA, with the western blot used as a follow-up test. The ELISA tests for antibodies, the body's defense system against infections; it does not test for the bacteria itself. These anti-Borrelia burgdorferi antibodies may take up to 2 to 6 weeks after infection to appear in the blood. Therefore, a blood test immediately following a tick bite will not be able to determine whether or not a person has been infected since not enough time has passed for antibodies to develop.

Other bacterial infections and diseases may cause an ELISA to be positive when, in fact, the patient does not have Lyme disease. Therefore, the Western Blot, a more accurate test that can be used 6 to 12 weeks after infection, is recommended to confirm all positive or equivocal ELISA results. However, if symptoms and history strongly suggest Lyme disease, a doctor may begin treatment without blood test confirmation. Note that frequent testing without symptoms that suggest infection, even in endemic areas, increases the chance of a test result being positive when a person is not actually infected with Lyme disease.

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