Cause and Risk Factors for Lyme Disease

Lyme disease is caused by infection with Borrelia burgdorferi bacteria. In the Northeast and North Central United States, the deer tick (Ioxodes scapularis) is responsible for transmission and in the Northwest, the western black-legged tick (Ioxodes pacificus) is the carrier.

The ticks that cause Lyme disease are very small. They live in wooded areas, low-growing grasslands near seashores, areas overgrown with brush, and in yards. The adult ticks are black or reddish and feed on blood by attaching themselves to a host.

The risk for contracting Lyme disease in the United States is highest in the coastal region of southern New England, the mid-Atlantic, and the Great Lakes. During the summer months, people who live or work outdoors (e.g., clearing brush, forestry, landscaping) in these areas are especially at risk. Ticks can also come into contact with people when they attach themselves to pets.

Outdoor activities that increase the risk for tick bite and infection include the following:

  • Camping
  • Fishing
  • Gardening
  • Hiking
  • Hunting
  • Picnicking

Publication Review By: John J. Swierzewski, D.P.M.

Published: 31 Dec 1999

Last Modified: 13 Aug 2015