Lyme disease: Symptoms, transmission, and treatment

Lyme disease, or borreliosis, is a potentially life-threatening condition that is transmitted to humans by blacklegged ticks.

The tick infects the person with the bacterium Borrelia burgdorferi (B. burgdorferi).

At first, a rash may appear. This can disappear without treatment, but in time, the person may develop problems with the joints, the heart, and the nervous system.

Lyme disease is the most common tick-borne infectious disease in the United States (U.S.). The ticks pick up the bacteria when they bite mice or deer that are carrying it.

It was first reported in 1977 in a town called Old Lyme, CT.

The Centers for Disease Control and Prevention (CDC) registered 25,435 confirmed cases of Lyme disease and 9,616 probable cases in 2015, an incidence of 8.9 cases in every 100,000 people.

The highest number was in Pennsylvania, with 7,351 confirmed cases. New England, the mid-Atlantic States, and the upper Midwest are most prone to ticks that can spread Lyme disease.

Fast facts on Lyme disease

Here are some key points about Lyme disease. More detail is in the main article.

Lyme disease is the most common tick-borne disease in the U.S.

The disease can only be passed on through the bites of certain kinds of tick.

A common symptom of Lyme disease is an erythema migrans rash.

Without effective treatment, symptoms disappear, but more severe symptoms can emerge weeks, months, or years later.


An erythema migrans (EM) rash should be reported to a doctor, as it may indicate Lyme disease.
An erythema migrans (EM) rash should be reported to a doctor, as it may indicate Lyme disease.

Initial signs and symptoms of Lyme disease are usually very mild. Some people may not notice any symptoms, or they may think they have flu.

After the initial phase, further symptoms develop. Symptoms can disappear, but the disease can affect the body in other ways, years later.

Stage 1: Early Lyme disease

Erythema migrans (EM) is a rash that often appears in the early stage of Lyme disease, from 3 to 30 days after infection, or 7 days on average.

EM affects 70 to 80 percent of people who are infected.

The rash:

typically begins as a small red area that expands over several days, to reach a diameter of 12 inches or 30 centimeters

may lose its color in the center, giving a bull’s-eye appearance

usually starts at the site of the tick bite but can appear elsewhere as the bacteria spread

is not painful or itchy but may feel warm to the touch

The rash may be less evident on darker skin.

Stage 2: Early disseminated Lyme disease

The rash will disappear after about 4 weeks, even without treatment, but other symptoms can emerge days to months after being bitten.

These include:

meningitis, or inflammation of the brain and spinal cord, leading to headaches and a stiff neck

additional rashes

fever and chills

swollen lymph nodes


pain in tendons, muscles, joints, and bones, especially in the large joints

heart palpitations or irregular heart beat

facial palsy, or loss of muscle tone in one or both sides of the face

dizziness and shortness of breath

nerve pain and shooting pains, numbness or tingling in the hands or feet

These symptoms may go away without treatment within a few weeks or months, but, in time, the person may experience further complications.

Anyone who may have Lyme disease should get medical help immediately. Early treatment is more effective.

Stage 3: Late disseminated Lyme disease

Also known as late Lyme disease, this may be the first sign of illness in some people.

Symptoms can emerge weeks, months, and even years after initial infection if a patient has not received treatment, or if antibiotic treatment has not been fully effective.

In some patients, this may be the first sign of illness.

It can involve problems with the nervous system and the heart.

The person may have:

difficulty concentrating

sleep and vision problems

memory loss

numbness, pain and tingling

irregular heart beat

joint pain

paralysis of the face muscles

Around 60 percent of untreated patients will experience recurrent bouts of arthritis with severe joint swelling, especially in the large joints.

Post-treatment Lyme Disease Syndrome

Even after treatment, a few people may experience post-treatment Lyme disease syndrome, sometimes referred to as chronic Lyme disease.

This involves nonspecific symptoms, such as fatigue and joint pain, that can persist for months after treatment.

Antibiotics are unlikely to help, so treatment aims to relieve symptoms, for example through rest and anti-inflammatory medications.

The symptoms should resolve in time.

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In the U.S, B. burgdorferi, the Lyme disease-causing bacterium, enters humans through the bite of an infected blacklegged tick, either Ixodes scapularis or Ixodes pacificus.

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