Clostridium tetani
Tetanus is often referred to as lockjaw due to the fact that the bacteria the causes it ("Clostridium tetani") cause the muscles of the jaw to tighten which makes the infected person unable to open their mouth. Today in the United States, tetanus is an uncommon disease with an average of only 29 cases reported per year between 1996 and 2009. Nearly all of these cases are of people who were never vaccinated for tetanus or adults who did not keep up to date with their boosters.