As a result of routine immunization, fewer than five cases of diphtheria are diagnosed per year in the United States.

• Low-income countries in Africa and Asia continue to have significant outbreaks; globally, there were ~7000 cases of diphtheria in 2008 and ~5000 deaths related to diphtheria in 2004.
• C. diphtheriae is transmitted via the aerosol route, primarily during close contact.
• Diphtheria toxin—the primary virulence factor—irreversibly inhibits protein synthesis, thereby causing the death of the cell.