Caused by the bacteria Borrelia burgdorferi. Deer ticks can carry the bacteria, and the disease is acquired after being bitten by an infected tick. Some patients don't remember the tick bite. There are three stages to the infection. See the symptoms section for a description. If untreated the disease can be serious involving the heart, brain, joints and nerves. The CDC states 94% of all Lyme disease cases occurred in the 12 states: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New Hampshire, New York, Pennsylvania, Virginia, and Wisconsin.