Lyme (LIME) disease is a tick-borne illness, the most common tick-borne illness in the United States. It is a bacterial disease that is spread to humans by the bite of an infected tick. It usually begins with a distinctive rash and/or flulike symptoms and, in some cases, can progress to a more serious disease with complications that affect multiple body systems.
Lyme disease was first described in 1977 when a group of children living in and around Lyme, Connecticut, became ill with arthritis. In its early stage, Lyme disease produces flulike symptoms. If untreated, the disease can progress to affect the joints, heart, and central nervous system * , especially in adults.
Lyme disease is caused by a corkscrew-shaped bacterium called Borrelia burgdorferi (buh-REEL-ee-uh burg-DOR-fe-ree). It is most commonly carried by very small, immature ticks of the genus Ixodes (iks-O-deez), familiarly called deer ticks, or black-legged ticks. Deer ticks spread Lyme disease in the Northeast, Midwest, and some other parts of the United States. Another kind of Ixodes tick, the western black-legged tick, is the source of Lyme disease in the western United States. Lyme disease also occurs in other countries, such as China, Japan, and some countries in Europe.
Lyme disease is not spread from person to person. It is spread by ticks that become infected with Borrelia burgdorferi after feeding on an animal, usually a mouse. Ticks then pass the bacteria to humans while attached to the person's skin and feeding on the person's blood. To infect a human, the tick must be attached for at least 24 hours. A bite by a tick does not mean that the individual will get Lyme disease; most tick bites do not cause disease.
Each year, approximately 30,000 cases of Lyme disease are reported to the Centers for Disease Control and Prevention (CDC) by state health departments and the District of Columbia. This number does not reflect every case of Lyme disease that is diagnosed in the United States every year. Research studies suggest that the actual number of people diagnosed with Lyme disease each year in the United States is around 300,000. Although cases of Lyme disease have been reported in nearly every state, Lyme disease cases are concentrated in the Northeast and upper Midwest, with 14 states accounting for over 96 percent of cases reported to the CDC. People who live, play, or work in tick-infested wooded areas or areas of overgrown brush are most at risk of getting the disease. Lyme disease is most common during the late spring and summer months in the United States (May through September), when ticks are most active and people are frequently outdoors.
Within a few days to weeks after being bitten by an infected tick, about 80 percent of people develop a characteristic red circular rash the size of a quarter or larger at the site of the bite. This rash is known as erythema migrans (air-uh-THEE-muh MY-granz). The center of the rash may clear as it grows, giving the appearance of a bull's-eye pattern. The rash may be warm to the touch, but it is usually not painful or itchy. Other symptoms in the early stage of Lyme disease may include tiredness, fever, chills, joint pain, muscle aches, headache, stiff neck, and swollen lymph nodes * (glands). Not everyone who is infected with the bacterium gets ill. Some people have no noticeable symptoms, and some only have the non-specific, flulike symptoms, such as fever and headache.
A late stage of Lyme disease may develop weeks to years after infection if the disease remains untreated. In this stage, symptoms can include chronic Lyme arthritis (episodes of pain and swelling in the joints, especially in the arms and legs), memory loss (which is rare in children and teens), and numbness in the hands, arms, legs, and feet.
Diagnosing Lyme disease can be difficult because the symptoms often look like those of other diseases. Doctors may have difficulty in distinguishing it from conditions with similar symptoms, particularly in cases in which the characteristic rash is not present. A known recent tick bite or the erythema migrans rash is often key to the diagnosis of Lyme disease. Following a physical examination and the taking of a medical history that includes questions about the patient's exposure to tick-infested areas, the doctor may order blood tests that look for the presence of antibodies * to Borrelia burgdorferi. If any joints are swollen or signs of meningitis are present, joint fluid or spinal fluid is sometimes evaluated for evidence of Borrelia infection.
Some blood tests for Borrelia infection can give false-negative results, particularly if performed within the first month after infection. False-positive test results can occur too. Because of this, doctors may have difficulty interpreting Lyme disease test results and confirming a diagnosis.
Lyme disease is usually treated with antibiotics * , which are taken for three to four weeks. Antibiotics used to treat Lyme disease are typically taken by mouth, but in severe or advanced cases, they may be given by injection. If treatment begins at the early stage of the disease, a complete cure is likely; it generally takes a few weeks or months for the symptoms to go away. Sometimes symptoms recur, making it necessary for a patient to take another course of antibiotics. If treatment is not started until later in the progression of the disease (at the early disseminated or late stage), antibiotics are still effective, but recovery may take longer; the patient's symptoms may last for months or even years. Children usually recover from Lyme disease faster and with fewer complications than do adults.
A person who is not ill may be treated preventively with a single dose of antibiotics if the following circumstances apply to the case:
The best way to prevent Lyme disease is to prevent tick bites. Experts recommend the avoidance of areas that are likely to be infested with ticks, particularly in the spring and summer when nymph (immature) ticks feed. For any activity in tick-infested areas, it is wise to take the following precautions:
Applying insect repellents containing 10 percent DEET * (which is safe to use on children and adults) on both clothes and exposed skin, as well as permethrin (per-ME-thrin) (which kills ticks on contact) on clothes, may also help reduce the risk of tick attachment. If ticks are found attached to skin, they should be carefully removed with tweezers or forceps.
Vaccines to prevent Lyme disease are under development, but as of 2016 were not available for use.
See also Bell's Palsy • Meningitis • Tick-Borne Illnesses: Overview
Barbour, Alan G. Lyme Disease: Why It's Spreading, How It Makes You Sick, and What to Do About It. Baltimore: Johns Hopkins University Press, 2015.
Horowitz, Richard. Why Can't I Get Better? Solving the Mystery of Lyme and Chronic Disease. New York: St. Martin's Press, 2013.
Centers for Disease Control and Prevention. “Lyme Disease.” http://www.cdc.gov/lyme/index.html (accessed March 15, 2016).
National Institute of Allergy and Infectious Diseases. “Lyme Disease.” (accessed March 15, 2016).
American Lyme Disease Foundation. PO Box 466, Lyme, CT 06371. Website: http://www.aldf.com (accessed March 15, 2016).
Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30333. Toll-free: 800-232-4636. Website: cdc.gov (accessed March 15, 2016).
Lyme Disease Association, Inc. PO Box 1438, Jackson, NJ 08527. Tollfree: 888-366-6611. Website: http://www.lymediseaseassociation.org (accessed March 15, 2016).
National Institute of Allergy and Infectious Diseases. Office of Communications and Public Liaison, 5601 Fishers Ln., MSC 9806, Bethesda, MD 20892-9806. Toll-free: 866-284-4107. Website: (accessed March 15, 2016).
* central nervous system is the part of the nervous system that includes the brain and spinal cord.
* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.
* Bell's palsy (PAWL-zee) is a condition in which there is weakness or loss of function of muscles on one side of the face.
* meningitis (meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.
* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.
* antibiotics (an-tee-by-AH-tiks) are drugs that kill or slow the growth of bacteria.
* endemic (en-DEH-mik) describes a disease or condition that is present in a population or geographic area at all times.
* DEET (abbreviation for N, N-Diethyl-meta-toluamide) is the active ingredient in many insect repellents.