There are over 800 species of ticks throughout the world, but only two families of ticks, Ixodidae (hard ticks) and Argasidae (soft ticks), are known to transmit diseases or illness to humans.
Learn where ticks live, how to prevent tick bites, and what to do after a tick bite. Homepage for CDC's website about ticks and tickborne diseases.
Overview Lyme disease is an illness caused by borrelia bacteria. Humans usually get Lyme disease from the bite of a tick carrying the bacteria. Ticks that can carry borrelia bacteria live throughout most of the United States. But Lyme disease is most common in the upper Midwest and the northeastern and mid-Atlantic states. It's also common in Europe and in south central and southeastern Canada.