Tetanus, also known as lockjaw, is a bacterial disease in which a toxin produced by anaerobic tetanus bacilli growing in contaminated wounds causes muscle spasm due to nerve toxicity. Minor cuts may be infected with the bacteria which are common in soil. The first symptom may often be painful contraction of the jaw and neck muscles; trunk muscles including those of respiration and muscles close to the site of injury are also frequently involved. Untreated, many cases are fatal, but artificial respiration, antiserum, and penicillin, have improved the outlook. Regular vaccination and adequate wound cleansing are important in prevention.