LYME DISEASE OVERVIEW
Lyme disease is the most common tick-borne illness in the United States and Europe. Lyme disease is caused by an infection with the bacteria, Borrelia burgdorferi, which is carried by deer ticks. The bacteria are transmitted when a tick bites a person.
Lyme disease was first described after an outbreak of what was thought to be "juvenile rheumatoid arthritis" in Lyme, Connecticut and surrounding communities. Since juvenile rheumatoid arthritis does not occur in outbreaks, researchers studied these patients, which led to the identification of Lyme arthritis, an infection that often affects the joints. As the researchers developed a better understanding of the infection, other non-joint features were identified. It became clear that Lyme disease affects different organs during different stages of the infection.
In most people, treatment with antibiotics is very effective in eliminating symptoms, preventing progression to later manifestations of the disease, and curing the infection. Some symptoms improve rapidly with this treatment, whereas other symptoms gradually improve over weeks to months.
This topic review discusses how Lyme disease develops, the symptoms, and the diagnostic process. A separate topic review discusses the treatment and prevention of Lyme disease. (See "Patient information: Lyme disease treatment (Beyond the Basics)" and "Patient information: Lyme disease prevention (Beyond the Basics)".) A topic review that discusses tick bites is also available (see "Patient information: What to do after a tick bite to prevent Lyme disease (Beyond the Basics)").
More detailed information about Lyme disease is available by subscription. (See "Clinical manifestations of Lyme disease in adults" and "Evaluation of a tick bite for possible Lyme disease" and "Lyme disease: Clinical manifestations in children" and "Diagnosis of Lyme disease" and "Prevention of Lyme disease" and "Treatment of Lyme disease".)
WHERE DOES LYME DISEASE OCCUR?
In the United States, Lyme disease commonly occurs in three regions: the northeast and mid-Atlantic states (from Maine to Virginia), the midwest (Minnesota, Wisconsin, and Michigan), and on the west coast (in northern California). (See "Epidemiology of Lyme disease".)
Although Lyme disease has been found in many states, more than 90 percent of cases in the United States have been reported from ten states: Massachusetts, Connecticut, Rhode Island, New York, New Jersey, Pennsylvania, Delaware, Maryland, Minnesota, and Wisconsin.
Within these states, there are "hot spots" where Lyme disease occurs most frequently; other locations in these states have a much lower rate of infection. These "hot spots" are the result of local environmental conditions.
The availability of food and water resources to the deer population is probably an important factor in the number of cases of Lyme disease. In addition, property at or near the border of forests is a preferred area for field mice, which carry deer ticks. Living in an area that borders a forest increases the risk of becoming infected with Lyme disease, especially for people who spend a lot of time outdoors.
Lyme disease also occurs in Europe and Asia (where it is often called Lyme borreliosis rather than Lyme disease). The signs and symptoms, organisms causing the disease, and ticks carrying the disease are somewhat different in Europe and Asia compared with the United States.
WHEN DOES LYME DISEASE OCCUR?
Infection with the bacteria that causes Lyme disease, Borrelia burgdorferi, usually occurs in the late spring and summer, particularly in a several week period around the time of the summer solstice, but some cases also occur in the early fall. Most people who become infected have the early features of infection; these symptoms typically occur within days to several weeks after the tick bite. Occasionally, a person does not recall the early illness and may be diagnosed after developing later features of infection. The peak season for becoming infected occurs during the nymphal stage of tick development, when the biting ticks are very small (about the size of a poppy seed) and trying to find food (human or animal blood). Due to their size, ticks are difficult to see (picture 1).
Lyme disease occurs less often in the late fall, and rarely in the winter and early spring because the small nymphal stage ticks are not seeking a blood meal at that time. In the fall, the adult stage ticks, which are about the size of a sesame seed, spread the infection. These larger ticks are more easily detected and can be removed before they bite. In addition, the adult stage ticks are less likely to transmit the Lyme disease bacteria than the nymphal ticks.
LYME DISEASE TRANSMISSION
Ticks are carried by mice (during the nymphal stage) and deer (in the adult stage). Ticks wait for a new host on the underside of low-lying shrubs and grass, often along the boundary between grass and the forest. Ticks are particularly dense in the shrubs and grass bordering paths frequented by deer. Ticks are also common in the gaps of old stone walls because field mice often nest in these areas.
Ticks do not survive for any length of time in sun-drenched lawns because they rapidly dry out. Ticks do not jump, hop, fly or descend from trees.
Ticks sense warmth and carbon dioxide given off by animals and humans as they pass the tick. Once the tick senses this warmth and carbon dioxide, it latches onto anything that brushes up against it.
Ticks take up to 24 hours from the time of first contact with the skin before they actually start to feed on the host's blood. The tick must remain firmly attached to the skin for 48 to 72 hours to pass the bacteria that causes Lyme disease to humans . Thus, there is a long period of time between the tick's first contact with its host and the transmission of infection.
An individual who is bitten by a tick has a very low risk (about 1 in 100 chance) of acquiring Lyme disease if the tick is removed before it is engorged (filled with blood). Thus, a careful search for ticks after spending time outdoors is useful in avoiding a tick bite; a tick that has not bitten cannot cause Lyme disease. (See "Patient information: Lyme disease prevention (Beyond the Basics)".)
LYME DISEASE RISK FACTORS
In regions of the United States where Lyme disease is common, individuals who spend a lot of time outdoors are at the greatest risk for Lyme disease, including people who work outdoors, garden, or participate in outdoor activities such as hunting or hiking.
There is a greater risk of acquiring Lyme disease in the area around old stone walls and between forest land and lawns, especially if the area contains low-lying shrubs or grasses.
Ticks can attach to pets (including dogs and cats) and be carried into the home. The tick can then infect the pet with Lyme disease, or, if the tick does not attach to the pet, it can become attached to a human and potentially transmit the infection.
LYME DISEASE SYMPTOMS
Symptoms of Lyme disease can vary widely and may include a rash at the site of the tick bite, flu-like symptoms, arthritis, heart symptoms, and neurologic symptoms. Infection causes few or no symptoms in a small percentage of people.
Symptoms are caused by the body's immune response to the bacteria and the inflammation that results; inflammation may continue even after treatment. Symptoms vary with the phase of the disease. The three phases are early localized, early disseminated, and late Lyme disease.
Early localized — Early localized Lyme disease causes a skin condition called erythema migrans (EM). EM typically occurs within one month of the tick bite, usually about 7 to 14 days after the tick bite, which may not have been noticed.
Erythema migrans — Erythema migrans (EM) is a distinctive skin rash that occurs at the site of the tick bite. The rash is usually salmon to red-colored; the color may cover the entire lesion or may have an area in the center that is flesh-colored. In some cases, the rash consists of multiple rings, which give it a "bull's eye" appearance (picture 2). The "bull's eye" is seen in about one-third of patients with EM. Approximately 80 percent of people develop EM, although only about 30 percent actually recall having had a tick bite.
The most common site for a tick bite is in the armpit, groin, backs of the knees, or belt line. Children may be bitten on the neck or scalp, although these are unusual sites for bites in adults. EM occasionally itches or burns. EM typically expands outward over several days and can be as large as 20 cm (8 inches) in diameter. The EM rash occasionally itches or burns. Most people have a single lesion (at the site of the tick bite), although about 10 to 20 percent have multiple lesions. This pattern is caused by the spread of the bacteria in the bloodstream rather than by multiple bites.
People with an allergy to tick saliva can develop a red rash at the site of the tick bite soon after being bitten; this rash typically lasts for 24 to 48 hours, but may continue for up to a week. This reaction may be confused with the EM rash. However, an allergic-type rash does not expand and typically becomes less red over time. In contrast, EM expands and often becomes more intensely red over time. When in doubt, a healthcare provider should be consulted. The provider can help distinguish between redness that does not require treatment and EM, which requires treatment.
Nonspecific symptoms — Early Lyme disease can cause nonspecific, virus-like signs and symptoms, including fatigue, a feeling of being unwell, fever, headache, muscle pain, joint pain, and swollen lymph nodes. However, these symptoms alone (without the presence of EM) are not sufficient to diagnose Lyme disease. Severe symptoms are unusual.
Early disseminated disease — During early disseminated Lyme disease, the bacteria spread through the bloodstream to other areas of the body, triggering inflammation in specific tissues. Early disseminated disease occurs days to weeks after the tick bite. Treatment at this stage helps to prevent later problems.
- Cardiac symptoms — Inflammation of the heart occurs in 8 percent or less of adults with untreated Lyme disease. This inflammation may interfere with the normal conduction of electrical impulses through the heart, causing a condition called atrioventricular block or heart block. Heart block can cause a slower than normal heart rate, lightheadedness and fainting, or may cause no symptoms at all.
Lyme disease may also cause inflammation of the heart muscle and the tissue covering the heart (myopericarditis), but these are rare symptoms and are usually mild when they do occur.
- Neurologic symptoms — Neurologic symptoms can result from inflammation of several areas of the nervous system, including:
- The meninges (the tissue covering the brain and spinal cord is called the meninges); inflammation of the meninges is called meningitis, which causes headache and a stiff neck.
- The nerve roots and nerves (especially the nerves that control facial movement), causing weakness, pain, or strange sensations, such as numbness.
These neurologic symptoms occur in about 10 percent of adult individuals with untreated Lyme disease.
Late disease — During late Lyme disease, inflammation most commonly affects the joints but may involve the nervous system and, in Europe, the skin. Symptoms of late Lyme disease occur months to years after a tick bite. In some individuals, these symptoms may be the first symptoms of the disease.
- Muscle and joint symptoms — Muscle and joint symptoms are the most common symptoms of late Lyme disease; these symptoms occur in 80 percent of individuals with Lyme disease who have not been treated with antibiotics. Joint pain occurs in 20 percent of individuals, intermittent episodes of arthritis (joint inflammation) in 50 percent, and persistent arthritis of a single joint (usually a knee) or a few joints in 10 percent of those who have not been treated.
- Neurologic symptoms — Late Lyme disease can cause a variety of neurologic symptoms including pain, difficulty with memory or thinking, and odd sensations, such as numbness. However, late neurologic manifestations of Lyme disease are quite rare, and therefore, these types of non-specific symptoms usually have causes other than Lyme disease.
- Skin symptoms — In Europe, the late symptoms of Lyme disease may include skin nodules. They may also include swelling and subsequent thinning of patches of skin, which usually occurs on the hands, feet, knees, or elbows.
Post-Lyme disease syndrome — Nonspecific symptoms such as headache, fatigue, and joint pain may linger for months after the treatment of Lyme disease has ended. However, these symptoms gradually resolve and do not require further antibiotic therapy.
The term "chronic" Lyme disease is not technically correct as there is no evidence that the bacteria can survive after appropriate antibiotic treatment. There is no evidence that antibiotics improve post-Lyme disease symptoms.
Fibromyalgia — Fibromyalgia develops in some people after treatment for Lyme disease. However, this is a post-infectious syndrome that is not caused by active infection with B. burgdorferi. Even in areas with high rates of Lyme disease, only a small number of all cases of fibromyalgia are actually triggered by prior infection with Lyme disease. Fibromyalgia is characterized by a specific pattern of muscle and joint pain. (See "Patient information: Fibromyalgia (Beyond the Basics)".)
LYME DISEASE DIAGNOSIS
The diagnosis of Lyme disease is based on an individual's history of possible exposure to ticks, the presence of characteristic signs and symptoms, and the results of blood tests. However, the results of blood tests for Lyme disease can vary from laboratory to laboratory. Results can be difficult to interpret if there is no history of tick exposure or EM. (See "Diagnosis of Lyme disease".)
Blood tests for Lyme disease are not recommended in people with nonspecific symptoms since tests may be falsely positive. Blood testing is also not recommended for a person who has classic features of early localized Lyme disease, including erythema migrans. Testing may be falsely negative during the first several weeks of infection, potentially delaying the correct diagnosis and treatment.
Blood tests — There are two major categories of blood tests, enzyme-linked immunosorbent assay (ELISA) and Western blot, which are used to check for current or prior infection with B. burgdorferi, the bacterium that causes Lyme disease. Both tests detect specific antibodies (proteins made by the immune system to fight the bacteria) made when the body's immune system responds to the organism that causes Lyme disease. Although the antibody responses decline slowly after adequate antibiotic treatment, the responses will remain positive even after antibiotic treatment. Thus, positive test results do not prove that the person has active infection.
Since it takes time for the immune system to respond to the infection and create antibodies, all antibody tests are less reliable in the early period after infection. As the infection progresses, virtually everyone with Lyme disease has a positive test result.
- ELISA — The ELISA is usually the first test done for Lyme disease. The ELISA test is very good (“sensitive”) at detecting antibodies to Lyme disease, but it can also detect antibodies against other proteins (low “specificity” for Lyme disease). When the ELISA detects antibodies in someone who does not have Lyme disease, it is called a “false positive” result. (Because of the chance of the ELISA giving a false positive result, a Western blot, which has improved specificity, is typically ordered to confirm a positive ELISA test.)
- Western blot — The second test, a Western blot, is done when the ELISA results are positive or equivocal (not clearly positive or negative); it is helpful in determining when the results of an ELISA test are falsely positive. The Western blot is more specific for B. burgdorferi than the ELISA because it identifies antigens individually; antigens are the parts of the Lyme disease bacteria that antibodies detect. The Western blot is typically reported as the number of antigens recognized (positive bands) out of the total tested. The greater the number of positive bands, the greater the chance that the patient has encountered the Lyme disease bacteria.
Cerebrospinal fluid tests — When a diagnosis of Lyme disease is uncertain and an individual has neurologic symptoms, testing the cerebrospinal fluid (the fluid surrounding the brain and spinal cord) using the ELISA and western blot can help to confirm the diagnosis.
Cerebrospinal fluid is collected by inserting a needle into the lower back, below where the spinal cord ends. This procedure is called a lumbar puncture or LP. The patient usually lies on an examining table, and is awake during the procedure. Local anesthetic (numbing medicine) is injected under the skin before the LP so that the patient feels only a pressure sensation. A small amount of fluid is collected and sent to a laboratory for testing.
LYME DISEASE TREATMENT AND PREVENTION
The treatment and prevention of Lyme disease are discussed in a separate topic. (See "Patient information: Lyme disease treatment (Beyond the Basics)" and "Patient information: Lyme disease prevention (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Lyme disease (The Basics)
Patient information: Insect bites and stings (The Basics)
Patient information: Rocky Mountain spotted fever (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Lyme disease treatment (Beyond the Basics)
Patient information: Lyme disease prevention (Beyond the Basics)
Patient information: What to do after a tick bite to prevent Lyme disease (Beyond the Basics)
Patient information: Fibromyalgia (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Clinical manifestations of Lyme disease in adults
Diagnosis of Lyme disease
Evaluation of a tick bite for possible Lyme disease
Epidemiology of Lyme disease
Musculoskeletal manifestations of Lyme disease
Prevention of Lyme disease
Treatment of Lyme disease
The following organizations also provide reliable health information.
- National Library of Medicine
(www.nlm.nih.gov/medlineplus/lymedisease.html, available in Spanish)
- National Institute of Allergy and Infectious Diseases
- National Center for Infectious Diseases
Division of Vector-Borne Infectious Diseases
- American Lyme Disease Foundation, Inc.