Lyme disease is an infection that is caused by the Borrelia burgdorferi bacterium, which is transmitted by the bite of the tiny deer tick. It is called Lyme disease because it was first diagnosed in Lyme, Connecticut, in 1975. The organism that causes it was discovered by Willy BurgdorferLyme disease is a vector-borne disease. This means it is transmitted from one host to another. When a tick carrying the Borrelia burgdorferi bacterium bites a person, the bacteria enter the skin and eventually spread through the lymph system or through the bloodstream. If someone is living in an area that is known to have a large tick population, or spend a great deal of time in wooded areas, use precautions to prevent tick bites. Wear light colored clothing on which ticks are more easily seen; wear a hat and tuck pant legs into your socks or boots to keep ticks out; use a tick repellent before going outdoors.