Lyme Disease


Lyme disease is a bacterial infection transmitted to humans by the bite of ticks infected with the spiralshaped bacterium Borrelia burgdorferi. The disease is characterized initially by a rash followed by flu-like symptoms, including fever, joint pain, and headache. The effects of this infection can be long term and disabling and can include chronic arthritis and nerve and heart dysfunction unless the infection is recognized and treated properly with antibiotics. Lyme disease is also called Lyme borreliosis.

The pathognomonic erythematous rash in the pattern of a bullseye, which manifested at the site of a tick bite on a woman's woman's posterior right upper arm. She subsequently contracted Lyme disease.

The pathognomonic erythematous rash in the pattern of a bullseye, which manifested at the site of a tick bite on a woman's woman's posterior right upper arm. She subsequently contracted Lyme disease.
(Centers for Disease Control and Prevention/Science Source)


Lyme disease affects men and women equally. People ages 5–14 and 45–54 are most likely to contract Lyme disease because these groups are more likely to participate in outdoor activities where they are exposed to ticks. About one-fourth of cases occur in children under age five. Lyme disease is reported more often in whites than any other race, likely because of increased exposure to tick-inhabited areas rather than any genetic predisposition.


Lyme is named for Lyme, Connecticut, the town where it was first diagnosed in 1975 after a puzzling outbreak of arthritis. The organism causing the disease is named for its discoverer, Willy Burgdorfer. Lyme disease, which is also called Lyme borreliosis, is a vector-borne disease, which means that it is delivered from one host, most often a small rodent or deer, to a human. It is also classified as a zoonosis, which is a disease of animals that can be transmitted to humans under natural conditions. In Lyme disease, a tick bearing the B. burgdorferi organism inserts it into a host's bloodstream when the tick bites the host to feed on its blood. Neither B. burgdorferi nor Lyme disease can be transmitted directly from one person to another or from pets to humans.

In the United States, Lyme disease accounts for more than 90% of all reported vector-borne illnesses. It is a significant public health problem and continues to be diagnosed in increasing numbers. The CDC attributes this increase to the growing size of the deer population and the geographical spread of infected ticks rather than to improved diagnosis.

Risk factors

People who spend a lot of time outdoors in wooded areas are at greatest risk of encountering ticks and developing Lyme disease. The risk for acquiring Lyme disease also depends on what stage in its life cycle a tick has reached. A tick passes through three stages of development—larva, nymph, and adult—each of which is dependent on a live host for food. In the United States, B. burgdorferi is carried by ticks of several species in the genus Ixodes, which usually feed on the white-footed mouse and deer and are often called deer ticks. In the summer, the larval ticks hatch from eggs laid in the ground and feed by attaching themselves to small animals and birds. At this stage they are not a problem for humans. In the next stage, the nymph causes most cases of Lyme disease. Nymphs are very active from spring through early summer, at the height of outdoor activity for most people. Because they are still quite small (less than 2 mm), they are difficult to spot, giving them ample opportunity to transmit B. burgdorferi while feeding. Many more adult ticks than nymphs carry B. burgdorferi; however, the adult ticks are much larger, more easily noticed, and more likely to be removed before the 24 hours or more of continuous feeding needed to transmit B. burgdorferi.

Causes and symptoms

Lyme disease is caused by B. burgdorferi. Once B. burgdorferi gains entry to the body through a tick bite, it can move through the bloodstream quickly. Only 12 hours after entering the bloodstream, B. burgdorferi can be found in cerebrospinal fluid, which means that it can affect the nervous system. Treating Lyme disease early and thoroughly is important because Lyme disease can persist for long periods within the body in a clinically latent (dormant) state. This persistence explains why symptoms can recur in cycles and can flare up after months or years, even over decades. It is important to note, however, that many people who are exposed to B. burgdorferi do not develop the disease.

Lyme disease usually is described in terms of length of infection (time since the person was bitten by a tick infected with Lyme disease) and whether B. burgdorferi is localized or disseminated (spread through the body by fluids and cells carrying B. burgdorferi). When and how symptoms of Lyme disease appear vary widely from patient to patient. People who experience recurrent bouts of symptoms over time are said to have chronic Lyme disease.

Early localized Lyme disease Late disseminated disease and chronic Lyme disease

Weeks, months, or even years after an untreated tick bite, symptoms can appear in several forms, including the following:

Less common effects of Lyme disease are heart abnormalities such as irregular rhythm (arrhythmias) or cardiac block and eye abnormalities such as swelling of the cornea, tissue, or eye muscles and nerves.

A late-stage complication of Lyme disease that affects the skin is acrodermatitis chronica atrophicans, a disorder in which the skin on the person's lower legs or hands becomes inflamed and paper-thin. This disorder is seen more frequently in Europe than in the United States.



A clear diagnosis of Lyme disease can be difficult and relies on information the patient provides and the doctor's clinical judgment, particularly through elimination of other possible causes of the symptoms. Lyme disease may mimic other conditions, including chronic fatigue syndrome (CFS), multiple sclerosis (MS), and other diseases with many symptoms involving multiple body systems. Differential diagnosis (distinguishing Lyme disease from other diseases) is based on clinical evaluation with laboratory tests used for clarification, when necessary.

Doctors generally know which disease-causing organisms are common in their geographic area. The most helpful piece of information is whether a tick bite or rash was noticed and whether it happened locally or while traveling. Doctors may not consider Lyme disease if it is rare locally but will take it into account if a patient mentions vacationing in an area where the disease is commonly found.

Children may have difficulty effectively verbalizing their symptoms, and thus their symptoms may be misdiagnosed. Parents who suspect Lyme disease in their children should inform their doctor about the possibility of the disease and be proactive in requesting further medical evaluation and treatment.


The CDC recommends a two-tiered blood testing procedure. These tests look for antibodies produced by the immune system in response to infection with B. burgdorferi rather than for the bacterium itself. The first test is either an enzyme-linked immunosorbent assay (ELISA) or an immunofluorescence assay (IFA) test. If either test is positive or the results are uncertain, a second blood test, the Western blot test, is recommended. If the first test is negative, the physician may perform additional tests to determine an alternate diagnosis.

Early diagnosis and prompt treatment are critical to preventing the neurologic complications of Lyme disease. Fewer than 50% of children realize that a tick has bitten them. Any child that develops a round, bull's-eye skin rash, joint pain, flu-like symptoms, and/or neurologic symptoms should see a doctor. Because the rash may not be readily visible (e.g., on the scalp under hair), children living in or visiting areas with a high incidence of Lyme disease and those participating in frequent outdoor activities during active tick months (generally May to November) who develop joint pain and neurologic symptoms should see a doctor. Adults also may miss the rash if it is located some place such as the back of the leg, so they should inspect their body regularly during warm months if they live in a high Lyme disease area.


Because most children do not realize they have been in tick-infested areas or been bitten by a tick and because deer ticks can be the size of a poppy seed or smaller, parents should be diligent about checking children for ticks, especially if the family lives in or visits an area with a high incidence of Lyme disease or an area near tick habitats.


For most patients, initial therapy consists of oral antibiotics such as doxycycline (Doryx, Vibramycin) or amoxicillin (Amoxil, Trimox) for 14–28 days. Penicillin is the antibiotic of choice for pregnant women and children under eight years of age. If there is poor response, alternative antibiotics are tried. When symptoms indicate nervous system involvement or a severe episode of Lyme disease, intravenous antibiotics such as ceftriaxone (Rocephin), cefotaxime (Claforan), or intravenous penicillin may be given for 14–30 days.

The physician may have to adjust the treatment regimen or change medications based on the patient's response. Treatment can be difficult because B. burgdorferi comes in several strains that may react differently to different antibiotics. Also, B. burgdorferi can shut itself up in cell niches, allowing it to hide from antibiotics. Finally, antibiotics can kill B. burgdorferi while it is active but now when it is latent.

Lyme disease during pregnancy

Untreated Lyme disease during pregnancy may lead to infection of the placenta and possibly a stillbirth. However, no adverse effects on a fetus had been found as of 2018 in cases in which the mother received appropriate antibiotic treatment for her Lyme disease. In general, treatment for pregnant women with Lyme disease is similar to that of non-pregnant adults, although certain antibiotics, such as doxycycline, that can affect fetal development should not be used because they can affect fetal development. As of 2018 there had been no cases reported of Lyme disease being transmitted through breast milk.

Alternative and complementary treatments

Alternative treatments are those that replace conventional pharmaceutical medicine. Complementary treatments are those used in conjunction with pharmaceutical medicine. There are no alternative treatments for Lyme disease. Antibiotic therapy is essential; however, complementary therapies may minimize symptoms of Lyme disease or improve the immune response. These include vitamin and nutritional supplements, mostly for chronic fatigue and increased susceptibility to infection. For example, yogurt and Lactobacillus acidophilus preparations help fight yeast infections, which are common in people on long-term antibiotic therapy. In addition, botanical medicine and homeopathy can be considered to help bring the body's systems back to a state of health and wellbeing. A Western herb, spilanthes (Spilanthes spp.), may have an effect on diseases such as Lyme disease that are caused by spirochetes (spiral-shaped bacteria), although as of 2018 this effect had not been proven to the satisfaction of practitioners of conventional medicine.

Other complementary therapies used in treating Lyme disease are:

A protein normally produced by the immune system to fight infection or rid the body of foreign material.
Any foreign substance, usually a protein, that stimulates the body's immune system to produce antibodies.
A disease caused by protozoa of the genus Babesia characterized by a malaria-like fever, anemia, vomiting, muscle pain, and enlargement of the spleen.
Bell's palsy—
Facial paralysis or weakness with a sudden onset, caused by swelling or inflammation of the seventh cranial nerve, which controls the facial muscles.
Cerebrospinal fluid (CSF)—
A clear fluid that fills the hollow cavity inside the brain and spinal cord. The cerebrospinal fluid has several functions, including providing a cushion for the brain against shock or impact and removing waste products from the brain.
Scattered or distributed throughout the body. Lyme disease that has progressed beyond the stage of localized EM is said to be disseminated.
ELISA protocols—
An acronym for enzyme-linked immunosorbent assay; a highly sensitive technique for detecting and measuring antigens or antibodies in a solution.
Erythema migrans (EM)—
A red skin rash that is one of the first signs of Lyme disease in about 75% of patients.
Lymph nodes—
Small, bean-shaped masses of tissue scattered along the lymphatic system that act as filters and immune monitors, removing fluids, bacteria, or cancer cells that travel through the lymph system.
Opportunistic infection—
An infection by organisms that usually do not cause infection in people whose immune systems are working normally.
An animal carrier that transfers an infectious organism from one host to another. The vector that transmits Lyme disease from wildlife to humans is the deer tick or black-legged tick.
Zoonosis (plural, zoonoses)—
Any disease of animals that can be transmitted to humans under natural conditions. Lyme disease and babesiosis are examples of zoonoses.

Public health role and response

Lyme disease is a reportable disease, with the requirements for reporting determined by state law. In most states, licensed healthcare providers, diagnostic laboratories, or hospitals report Lyme disease cases. All personally identifiable information is removed from the reports before the information is provided to the CDC, which compiles and publishes the national surveillance data. The goal of Lyme disease surveillance is not to capture every case but to systematically gather and analyze public health data in a way that enables public health officials to look for trends and take actions to reduce the disease and improve public health.

The CDC has developed a program of service, research, and education focusing on the prevention and control of Lyme disease. Activities of this program include:

Many states in the United States have also developed educational programs concerning Lyme disease for their citizens.




Minimizing risk of exposure

Precautions to avoid contact with ticks include moving leaves and brush away from living quarters. Most important are personal protection techniques when outdoors, such as the following.

Minimizing risk of disease

The two most important factors are removing the tick quickly and carefully and seeking a doctor's evaluation at the first sign of symptoms of Lyme disease. When in an area that may be tick-populated, people should take the following steps:

A vaccine for Lyme disease was available from 1998 to 2002, when it was removed from the U.S. market. Protection provided by the vaccine fades over time. Anyone who was vaccinated at the time the vaccine was available likely no longer has protection against the disease. A vaccine still exists for dogs, although veterinarians have mixed views about its usefulness.

See also Tick-borne diseases .



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Horowitz, Richard I. How Can I Get Better? An Action Plan for Treating Resistant Lyme and Chronic Disease. New York: St. Martin's Griffin, 2017.

Tokarz, Rafal. The Everything Guide to Lyme disease. Avon, MA: Simon & Schuster, 2018.


Dimeo-Ediger, Winona. “Lyme Disease: Inside America's Mysterious Epidemic.” Rolling Stone June 20, 2017. (accessed April 20, 2018).


Meyerhoff, John. “Lyme Disease.” Medscape. (accessed April 20, 2018).

U.S. Centers for Disease Control and Prevention. “Lyme Disease.” (accessed April 20, 2018).

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American Lyme Disease Foundation, PO Box 466, Lyme, CT, 06371,, .

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd., Atlanta, GA, 30329-4027, (404) 639-3534, (800) 232-4636; TTY: 888-232-6348, .

Jennifer E. Sisk, MA
Revised by Tish Davidson, AM

  This information is not a tool for self-diagnosis or a substitute for professional care.