Lyme disease is a bacterial infection. The infection is spread from the bite of an infected deer tick.

Lyme disease is caused by bacteria found in some deer ticks. An infected tick passes Lyme disease to humans through its bite.

If untreated, the bacteria can pass into the blood. The blood will carry it through the body. The bacteria may then settle in various body tissues. The spread of the infection can cause a number of symptoms, ranging from mild to severe.