Fusobacterium is a genus of anaerobic bacteria commonly found in the human mouth and gastrointestinal tract. These bacteria are rod-shaped and play a role in the normal flora of the body. However, some species can be associated with various infections, including periodontal disease and certain systemic conditions. Infections caused by Fusobacterium can occur when these bacteria enter the bloodstream or other normally sterile areas of the body. They are often implicated in conditions such as Lemierre's syndrome, a rare but serious illness characterized by thrombophlebitis and septic emboli. Proper oral hygiene can help reduce the risk of infections related to Fusobacterium.