What is Lyme Disease?
Lyme disease (LD) is an infection caused by Borrelia burgdorferi, a type of bacterium called a spirochete (pronounced spy-ro-keet) that is carried by deer ticks(Click here for pictures of deer ticks). An infected tick can transmit the spirochete to the humans and animals it bites. Untreated, the bacterium travels through the bloodstream, establishes itself in various body tissues, and can cause a number of symptoms, some of which are severe. Often, an erythema migrans (EM) rash appears within 7-14 days at the site of a tick bite (click to see picture of a typical EM rash).
LD manifests itself as a multisystem inflammatory disease that affects the skin in its early, localized stage, and spreads to the joints, nervous system and, to a lesser extent, other organ systems in its later, disseminated stages. If diagnosed and treated early with antibiotics, LD is almost always readily cured. Generally, LD in its later stages can also be treated effectively, but because the rate of disease progression and individual response to treatment varies from one patient to the next, some patients may have symptoms that linger for months or even years following treatment. In rare instances, LD causes permanent damage.
Although LD is now the most common arthropod-borne illness in the U.S. (more than 150,000 cases have been reported to the Centers for Disease Control and Prevention [CDC] since 1982), its diagnosis and treatment can be challenging for clinicians due to its diverse manifestations and the limitations of currently available serological (blood) tests.
The prevalence of LD in the northeast and upper mid-west is due to the presence of large numbers of the deer tick’s preferred hosts – white-footed mice and deer – and their proximity to humans. White-footed mice serve as the principal “reservoirs of infection” on which many larval and nymphal (juvenile) ticks feed and become infected with the LD spirochete. An infected tick can then transmit infection the next time it feeds on another host (e.g., an unsuspecting human).
The LD spirochete, Borrelia burgdorferi, infects other species of ticks but is known to be transmitted to humans and other animals only by the deer tick (also known as the black-legged tick) and the related Western black-legged tick. Studies have shown that an infected tick normally cannot begin transmitting the spirochete until it has been attached to its host about 36-48 hours; the best line of defense against LD, therefore, is to examine yourself at least once daily and remove any ticks before they become engorged (swollen) with blood.
Generally, if you discover a deer tick attached to your skin that has not yet become engorged, it has not been there long enough to transmit the LD spirochete. Nevertheless, it is advisable to be alert in case any symptoms do appear; a red rash (especially surrounding the tick bite), flu-like symptoms, or joint pains in the first month following any deer tick bite could signal the onset of LD.
Manifestations of what we now call Lyme disease were first reported in medical literature in Europe in 1883. Over the years, various clinical signs of this illness have been noted as separate medical conditions: acrodermatitis, chronica atrophicans (ACA), lymphadenosis benigna cutis (LABC), erythema migrans (EM), and lymphocytic meningradiculitis (Bannwarth’s syndrome). However, these diverse manifestations were not recognized as indicators of a single infectious illness until 1975, when LD was described following an outbreak of apparent juvenile arthritis, preceded by a rash, among residents of Lyme, Connecticut.
Where is Lyme Disease Prevalent?
LD is spreading slowly along and inland from the upper east coast, as well as in the upper midwest. The mode of spread is not entirely clear and is probably due to a number of factors such as bird migration, mobility of deer and other large mammals, and infected ticks dropping off of pets as people travel around the country. It is also prevalent in northern California and Oregon coast, but there is little evidence of spread.
In order to assess LD risk you should know whether infected deer ticks are active in your area or in places you may visit. The population density and percentage of infected ticks that may transmit LD vary markedly from one region of the country to another. There is even great variation from county to county within a state and from area to area within a county. For example, less than 5% of adult ticks south of Maryland are infected with B. burgdorferi, while up to 50% are infected in hyperendemic areas (areas with a high tick infection rate) of the northeast. The tick infection rate in Pacific coastal states is between 2% and 4%.
To view most recent data, click here.
Symptoms of Lyme Disease
The spirochetal agent of Lyme disease, Borrelia burgdoferi, is transmitted to humans through a bite of a nymphal stage deer tick Ixodes scapularis (or Ixodes pacificus on the West Coast). The duration of tick attachment and feeding is a key factor in transmission. Proper identification of tick species and feeding duration aids in determining the probability of infection and the risk of developing Lyme disease.
The early symptoms of LD can be mild and easily overlooked. People who are aware of the risk of LD in their communities and who do not ignore the sometimes subtle early symptoms are most likely to seek medical attention and treatment early enough to be assured of a full recovery.
The first symptom is usually an expanding rash (called erythema migrans, or EM, in medical terms) which is thought to occur in 80% to 90% of all LD cases. An EM rash generally has the following characteristics:
- Usually (but not always) radiates from the site of the tickbite
- Appears either as a solid red expanding rash or blotch, OR a central spot surrounded by clear skin that is in turn ringed by an expanding red rash (looks like a bull’s-eye)
- Appears an average of 1 to 2 weeks (range = 3 to 30 days) after disease transmission
- Has an average diameter of 5 to 6 inches
(range = 2 inches to 2 feet)
- Persists for about 3 to 5 weeks
- May or may not be warm to the touch
- Is usually not painful or itchy
EM rashes appearing on brown-skinned or sun-tanned patients may be more difficult to identify because of decreased contrast between light-skinned tones and the red rash. A dark, bruise-like appearance is more common on dark-skinned patients.
Ticks will attach anywhere on the body, but prefer body creases such as the armpit, groin, back of the knee, and nape of the neck; rashes will therefore often appear in (but are not restricted to) these areas. Please note that multiple rashes may, in some cases, appear elsewhere on the body sometime after the initial rash, or, in a few cases, in the absence of an initial rash.
Around the time the rash appears, other symptoms such as joint pains, chills, fever, and fatigue are common, but they may not seem serious enough to require medical attention. These symptoms may be brief, only to recur as a broader spectrum of symptoms as the disease progresses.
As the LD spirochete continues spreading through the body, a number of other symptoms including severe fatigue, a stiff, aching neck, and peripheral nervous system (PNS) involvement such as tingling or numbness in the extremities or facial palsy (paralysis) can occur.
The more severe, potentially debilitating symptoms of later-stage LD may occur weeks, months, or, in a few cases, years after a tick bite. These can include severe headaches, painful arthritis and swelling of joints, cardiac abnormalities, and central nervous system (CNS) involvement leading to cognitive (mental) disorders.
The following is a checklist of common symptoms seen in various stages of LD:
Localized Early (Acute) Stage:
- Solid red or bull’s-eye rash, usually at site of bite
- Swelling of lymph glands near tick bite
- Generalized achiness
Early Disseminated Stage:
- Two or more rashes not at site of bite
- Migrating pains in joints/tendons
- Stiff, aching neck
- Facial palsy (facial paralysis similar to Bell’s palsy)
- Tingling or numbness in extremities
- Multiple enlarged lymph glands
- Abnormal pulse
- Sore throat
- Changes in vision
- Fever of 100 to 102 F
- Severe fatigue
- Arthritis (pain/swelling) of one or two large joints
- Disabling neurological disorders (disorientation; confusion; dizziness; short-term memory loss; inability to concentrate, finish sentences or follow conversations; mental “fog”)
- Numbness in arms/hands or legs/feet
Diagnosis of Lyme Disease
If you think you have LD symptoms you should see your physician immediately. The EM rash, which may occur in up to 90% of the reported cases, is a specific feature of LD, and treatment should begin immediately.
Even in the absence of an EM rash, diagnosis of early LD should be made on the basis of symptoms and evidence of a tick bite, not blood tests, which can often give false results if performed in the first month after initial infection (later on, the tests are more reliable). If you live in an endemic area, have symptoms consistent with early LD and suspect recent exposure to a tick, present your suspicion to your doctor so that he or she may make a more informed diagnosis.
If early symptoms are undetected or ignored, you may develop more severe symptoms weeks, months or perhaps years after you were infected. In this case, the CDC recommends using the ELISA and Western-blot blood tests to determine whether you are infected. These tests, as noted above, are considered more reliable and accurate when performed at least a month after initial infection, although no test is 100% accurate.
If you have neurological symptoms or swollen joints your doctor may, in addition, recommend a PCR (Polymerase Chain Reaction) test via a spinal tap or withdrawal of synovial fluid from an affected joint. This test amplifies the DNA of the spirochete and will usually indicate its presence.
Issues and Insights Related to the Diagnosis of Lyme Disease:
2-tired Antibody Testing for Early and Late Lyme Disease Using Only and Immunoglobulin G Blot with the Addition of a VlsE Band and the Second-tier Test Rapid, Simple, Quantitative , and Highly Sensitive Antibody Detection for Lyme Disease
Updates and Recent Reports
Announcements from the FDA and CDC on the Diagnosis of Lyme Disease
Recommended courses and duration of treatment for both early and late Lyme symptoms are shown in our Table of Recommended Antibiotics and Dosages (see also table footnotes).
Early treatment of LD (within the first few weeks after initial infection) is straightforward and almost always results in a full cure. Treatment begun after the first three weeks will also likely provide a cure, but the cure rate decreases the longer treatment is delayed.
Doxycycline, amoxicillin and ceftin are the three oral antibiotics most highly recommended for treatment of all but a few symptoms of LD. A recent study of Lyme arthritis in the New England Journal of Medicine indicates that a four-week course of oral doxycycline is just as effective in treating late LD, and much less expensive, than a similar course of intravenous Ceftriaxone (Rocephin) unless neurological or severe cardiac abnormalities are present. If these symptoms are present, the study recommends immediate intravenous (IV) treatment.
Treatment of late-Lyme patients can be more complicated. Usually LD in its later stages can be treated effectively, but individual variation in the rate of disease progression and response to treatment may, in some cases, render standard antibiotic treatment regimens ineffective. In a small percentage of late-Lyme patients, the disease may persist for many months or even years. These patients will experience slow improvement and resolution of their persisting symptoms following oral or IV treatment that eliminated the infection.
Although treatment approaches for patients with late-stage LD have become a matter of considerable debate, many physicians and the Infectious Disease Society of America recognize that, in some cases, several courses of either oral or IV (depending on the symptoms presented) antibiotic treatment may be indicated. However, long-term IV treatment courses (longer than the recommended 4-6 weeks) are not usually advised due to adverse side effects. While there is some speculation that long-term courses may be more effective than the recommended 4-6 weeks, there is currently no scientific evidence to support this assertion. Click here for an article from the New England Journal of Medicine which presents clinical recommendations in the treatment and prevention of early Lyme disease.
More Information on Treatment Guidelines
Dangers of Long-Term Antibiotic Treatment for Lyme Disease.
Current Clinical Studies
NIAID Clinical Trials
Two Controlled Trials of Antibiotic Treatment in Patients with Persistent Symptoms and a History of Lyme Disease ( The above clinical trials were conducted under the following protocols that were approved by the NIAID Clinical Studies Group, the Institutional Review Board, the NIAID Biostatistics Group, and the Food and Drug Administration (FDA) before the trails were conducted. To ensure complete compliance with the protocols, all procedures associated with the trials were carefully monitored by an independent Data Safety and Monitoring Board (DSMB) that included several distinguished biostatisticians. Note that the protocols stipulated that an interim statistical analysis be performed when 100 subjects have been enrolled.)
Research and Clinical Studies
Editor’s Note: Since ceftriaxone has been reported to have profound neuroprotective effects (Nature 433: 73-77, 2005) and is often used to treat Lyme disease with neurological complications, clinical studies are now in progress to assess its efficacy in the treatment of ALS.
A Case Revealing the Natural History of Untreated Lyme Disease ( Although the data are not shown in the publication, the author confirms that the IgG Western blot was positive by the CDC criteria and showed the presence of 21,28,30,39,41,45,58,66, and 93 kDa bands. )
How to Evaluate the Claims About Cures and Treatments for Long-term, Chronic Conditions
Studies on Chronic Lyme Disease Syndromes
News Articles and Commentaries
Peer-Reviewed Scientific Publications
Clinical Trials on the Efficacy of Extended Antibiotic Therapy
Two Controlled Trials of Antibiotic Treatment in Patients with Persistent Symptoms
and a History of Lyme Disease ( The above clinical trials were conducted under the following protocols that were approved by the NIAID Clinical Studies Group, the Institutional Review Board, the NIAID Biostatistics Group, and the Food and Drug Administration (FDA) before the trails were conducted. To ensure complete compliance with the protocols, all procedures associated with the trials were carefully monitored by an independent Data Safety and Monitoring Board (DSMB) that included several distinguished biostatisticians. Note that the protocols stipulated that an interim statistical analysis be performed when 100 subjects have been enrolled.)
Time for a different approach to Lyme disease and long-term symptoms
(For additional perspective on this important issue, see “The Pain of Chronic Lyme Disease: Moving the Discourse in a Different Direction“)
Lyme Disease and Co-Infections
Commentaries and Reviews on Lyme Disease
From the Desk of the Executive Director
- Ending the Lyme Disease Wars
- Chronic Lyme Disease: in Defense of the Scientific Enterprise
- Lyme Borreliosis is not Sexually Transmitted
- The Pain of Chronic Lyme Disease: Moving the Discourse in a Different Direction
- What do the Experts Recommend about the Treatment of Lyme Disease?
- Borreliaburgdorferi vs Treponema pallidum – what’s in a name?
- There is no published evidence supporting the diagnosis of chronic, atypical tick-borne co-infections in patients diagnosed with chronic Lyme disease.
- The results of European studies show that patients with early Lyme disease are rarely co-infected with other tick-transmitted agents.
- Understanding Chronic Pain
- Vaccines against Lyme disease: what happened and what lessons can we learn?
- Understanding Antibody-based Diagnostic Tests for Lyme Disease
- Popular antibiotics may carry serious side effect.
- The Media Must Exercise Greater Responsibility in Reporting Information on Lyme Disease
- Is there a need to conduct still more clinical trials on the benefit of extended antibiotic therapy for the treatment of persistent post-treatment symptoms of Lyme disease?
- What Can One Learn That is Clinically Relevant from the Results of in vitro Studies on Persisters?
- Jarisch-Herxheimer and Lyme Disease
- Straight Talk About Chronic Lyme Disease
- Does Chronic Rocky Mountain Spotted Fever (RMSF) Exist?
- There are more than 300 medical conditions with symptoms like those often associated with Lyme disease
- Light at the End of the Tunnel
Quiz on Lyme Disease
Lyme Disease Stories
Unorthodox Treatments Being Promoted to Treat Lyme Disease
Readers should note that there is no published, peer-reviewed evidence to indicate that any of the treatments presented in this incomplete listing is beneficial for the treatment of Lyme disease and/or “chronic Lyme disease”. In fact, some of them may even be unsafe when used a prescribed. Consequently, the reader is urged to demand to see documented evidence of their benefit before even considering their use. This listing in no way implies endorsement by the American Lyme Disease Foundation.
Informative videos about Lyme Disease