The National Academies

The National Academies: What You Need To Know About Infectious Disease

What You Need To Know About Infectious Disease

Lyme Disease

Lyme disease is an inflammatory disease caused by the bacterium Borrelia burgdorferi, which normally lives in small rodents and deer. It is transmitted among these animals—and to humans—through the bites of infected blacklegged ticks.

Lyme disease was first reported in the United States in the town of Old Lyme, Connecticut, in 1975. Although cases have been reported throughout the United States, most occur in the Northeast, some parts of Minnesota and Wisconsin, and the Mid-Atlantic states. For example, in 2014, 96 percent of cases were reported in 14 states, including Connecticut, Delaware, Maine, Maryland, and Massachusetts. Lyme disease is usually seen from late spring through early fall.

Early symptoms of Lyme disease, which typically occur within 3 to 30 days after the tick bite, include fever, chills, headache, fatigue, muscle and joint pain, and swollen lymph nodes. In some cases, these may be the only symptoms of infection. A circular rash called erythema migrans (EM), may appear around the site of the tick bite looks like a bull’s-eye. A distinctive feature of the rash is that it gradually expands over a period of several days, reaching up to 12 inches across 

If left untreated, the infection may spread to other parts of the body within days or months, producing an array of discrete symptoms. These include facial or Bell’s palsy, loss of muscle tone or droop on one or both sides of the face; severe headaches and neck stiffness ; additional EM rashes on the body; severe joint pain and swelling, particularly in the knees and other large joints; heart palpitations or an irregular heartbeat; intermittent pain in the tendons, muscles, joints, and bones; episodes of dizziness or shortness of breath; inflammation of the brain and spinal cord; nerve pain; shooting pain, numbness, or tingling in the hands and feet; and problems with short-term memory. 

In order to become infected with Lyme disease, an individual must be bitten by a blacklegged tick. This is more likely to occur if the bite occurred in a state with large number of these ticks. After being bitten, it is important to remove the tick as soon as possible. If the illness is identified during the early stages of the infection, individuals treated with antibiotics usually recover rapidly and completely.

In a small percentage of cases, a person will continue having symptoms that can interfere with daily life. This condition is called “Post-Treatment Lyme Disease Syndrome” (PTLDS). The National Institutes of Health has studied the effects of long-term use of antibiotics for individuals with PTLDS. This approach has not been shown to be effective. Researchers are continuing to investigate ways to treat people with a more chronic form of the disease.

Reducing exposure to ticks is the best way to prevent Lyme disease infections. This can be done by wearing long-sleeved pants and shirts and high boots when outside. Using insect repellant on all exposed skin and clothing can also help reduce exposure. Because the ticks that can carry Lyme disease are so tiny, it is important to remove all clothes and inspect all skin surfaces after returning home from a place where ticks are prevalent. Taking a bath or shower within 2 hours after returning from being outdoors can help remove any ticks on the body. To remove ticks from clothing worn while outside, either wash in hot water or put them in the dryer on high heat for 10 minutes

Ticks often attach to pets as well. Therefore, it is important to use a tick preventive product on your pet, to check pets for ticks daily, and to remove any ticks you may find as soon as possible. Finally, to help keep people and pets safe from ticks at home, clear tall grasses and brush from the yard, mow the lawn frequently, keep leaves raked, and create a barrier to help keep animals carrying ticks from entering your yard.


Explore Other Topics

What do you know about infectious disease?

True or False: Infection with a pathogen (a disease-causing microbe) does not necessarily lead to disease.

  • Correct!

    Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.

  • Sorry, that’s incorrect.

    Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.

Infectious Disease Defined

Skin Lesion

Any abnormal tissue on the skin caused by injury or disease.

View our full glossary