Lyme disease is the most common vector-borne disease in the United States. Lyme disease is caused by the bacterium Borrelia burgdorferi and rarely, Borrelia mayonii. It is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. Lyme disease is diagnosed based on symptoms, physical findings (e.g., rash), and the possibility of exposure to infected ticks. Laboratory testing is helpful if used correctly and performed with validated methods. Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics. Steps to prevent Lyme disease include using insect repellent, removing ticks promptly, applying pesticides, and reducing tick habitat. The ticks that transmit Lyme disease can occasionally transmit other tickborne diseases as well.
Signs and Symptoms of Untreated Lyme Disease
Early Signs and Symptoms (3 to 30 Days After Tick Bite)
The appearance of the erythema migrans rash can vary widely.
- Fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes may occur in the absence of rash
- Erythema migrans (EM) rash (see photos):
- Occurs in approximately 70 to 80 percent of infected persons
- Begins at the site of a tick bite after a delay of 3 to 30 days (average is about 7 days)
- Expands gradually over several days reaching up to 12 inches or more (30 cm) across
- May feel warm to the touch but is rarely itchy or painful
- Sometimes clears as it enlarges, resulting in a target or “bull’s-eye” appearance
- May appear on any area of the body
- Does not always appear as a “classic” erythema migrans rash
Photos of RashesLater Signs and Symptoms (days to months after tick bite)
- Severe headaches and neck stiffness
- Additional EM rashes on other areas of the body
- Facial palsy (loss of muscle tone or droop on one or both sides of the face)
- Arthritis with severe joint pain and swelling, particularly the knees and other large joints.
- Intermittent pain in tendons, muscles, joints, and bones
- Heart palpitations or an irregular heart beat (Lyme carditis)
- Episodes of dizziness or shortness of breath
- Inflammation of the brain and spinal cord
- Nerve pain
- Shooting pains, numbness, or tingling in the hands or feet
Diagnosis and TestingMore about rashes
- A small bump or redness at the site of a tick bite that occurs immediately and resembles a mosquito bite, is common. This irritation generally goes away in 1-2 days and is not a sign of Lyme disease.
- A rash with a very similar appearance to EM occurs with Southern Tick-associated Rash Illness (STARI), but is not Lyme disease
- Ticks can spread other organisms that may cause a different type of rash
Diagnosis and Testing
New! APHL Guidance and Interpretation of Lyme Disease Serologic Test Results
This report describes the proper interpretation of serologic testing for B. burgdorferi and identifies best practices for reporting results to clinicians, public health agencies, and patients.external iconMore
When assessing a patient for Lyme disease, health care providers should consider:
- The signs and symptoms of Lyme disease
- The likelihood that the patient has been exposed to infected blacklegged ticks
- The possibility that other illnesses may cause similar symptoms
- Results of laboratory tests, when indicated
CDC currently recommends a two-step testing process for Lyme disease. Both steps are required and can be done using the same blood sample. If this first step is negative, no further testing is recommended. If the first step is positive or indeterminate (sometimes called “equivocal”), the second step should be performed. The overall result is positive only when the first test is positive (or equivocal) and the second test is positive (or for some tests equivocal).
Key points to remember
- Most Lyme disease tests are designed to detect antibodies made by the body in response to infection.
- Antibodies can take several weeks to develop, so patients may test negative if infected only recently.
- Antibodies normally persist in the blood for months or even years after the infection is gone; therefore, the test cannot be used to determine cure.
- Infection with other diseases, including some tickborne diseases, or some viral, bacterial, or autoimmune diseases, can result in false positive test results.
- Some tests give results for two types of antibody, IgM and IgG. Positive IgM results should be disregarded if the patient has been ill for more than 30 days.
CDC supports the development of new tests
New tests may be developed as alternatives to one or both steps of the two-step process. Before CDC will recommend new tests, they must be cleared by the Food and Drug Administration (FDA). For more details, see: Recommendations for Test Performance and Interpretation from the Second National Conference on Serologic Diagnosis of Lyme Disease.