Tetanus

Overview, Causes, & Risk Factors

Spores of the bacterium Clostridium tetani live in the soil and are found around the world. In the spore form, C. tetani may remain dormant in the soil, and it can remain infectious for more than 40 years.

Tetanus causes approximately five deaths per year in the U.S. Internationally, reports show up to 1 million cases annually, mostly in developing countries. Tetanus infections in newborns accounts for about half of tetanus-related deaths in developing countries.

Infection begins when the spores are introduced into an injury or wound. The spores germinate, releasing active bacteria that multiply and produce a neurotoxin called tetanospasmin. Tetanospasmin selectively blocks inhibitory nerve transmission from the spinal cord to the muscles, allowing the muscles to go into severe spasm. Spasmodic contractions may be so powerful that they tear the muscles or cause compression fractures of the vertebrae.

Tetanus often begins with mild spasms in the jaw muscles (trismus), neck muscles, and facial muscles. Stiffness rapidly develops in the chest, back, abdominal muscles, and sometimes the laryngeal muscles (which then interferes with breathing). Muscular seizures (tetany) cause sudden, powerful, and painful contraction of muscle groups. These episodes can cause fractures and muscle tears.

Without treatment, one out of three affected people die. The mortality rate for newborns with untreated tetanus is even higher: two out of three. With proper treatment, less than 10% of infected patients die.

The incubation period is five days to 15 weeks, with seven days as the average. About 100 cases of tetanus occur every year in the U.S., the vast majority in un-immunized individuals or those whose last immunization was no longer current. In developing countries, tetanus frequently causes death in newborn infants when the umbilical stump becomes infected.