Tetanus is a rare disease in developed countries. The incidence of tetanus ranges from 10,000 to 1 million cases per year globally, with only 50–100 of those cases occurring in the United States. Success in prevention of tetanus is largely due to vaccination programs. In developed countries, tetanus is most commonly seen in older persons, recent immigrants, and IV drug users who have not maintained adequate tetanus immunization. Tetanus is caused by an exotoxin produced by Clostridium tetani, an anaerobic, spore-forming, gram-positive rod found widely in soil and in the GI tract.