Lyme disease is an infection that is transmitted through the bite of a tick infected with a bacterium called Borrelia burgdorferi. Ticks typically get the bacterium by biting infected animals, like deer and mice.Most people who get tick bites do not get Lyme disease.yme disease is an infection that is transmitted through the bite of a tick infected with a bacterium called Borrelia burgdorferi. Ticks typically get the bacterium by biting infected animals, like deer and mice.