Lyme disease is an infectious disease caused by the bacteria Borrelia burgdorferi. B. burgdorferi is transmitted to humans by biting an infected black-legged or deer tick. The tick becomes infected after feeding on infected deer, birds, or mice.

A tick has to be present on the skin for at least 36 hours to transmit the infection. Many people with Lyme disease have no memory of a tick bite.

Lyme disease was first recognized in the town of Old Lyme, Connecticut, in 1975. It’s the most common tick-borne illness in Europe and the United States.

People who live or spend time in wooded areas known for disease transmission are more likely to get this illness. People with domesticated animals visiting wooded regions also have a higher risk of developing Lyme disease.

Cases of Lyme disease have varied yearly but have steadily increased for the past 20 years in the United States.

Lyme disease is not common in all United States and is primarily concentrated in the Northeast and upper Midwest regions.