Lyme disease is a worldwide, tick-transmitted spirochetosis. Borrelia burgdorferi is the etiologic bacterium and the vector is a tick of the genus Ixodes.
Ticks are tiny spider-like creatures found in woodland and heath areas. They feed on the blood of birds and mammals, including humans. The seasonal pattern of tick activity determines the seasonal pattern of illness onset; symptoms typically begin in late spring or summer. Because ticks prefer forest underbrush, illness is more common in such areas.