Causes and Transmission
Tetanus is an infection caused by a bacterium called Clostridium tetani. Spores of tetanus bacteria are everywhere in the environment, including soil, dust, and manure. The spores develop into bacteria when they enter the body.
Stepping on nails or other sharp objects is one way people are exposed to the bacteria that cause tetanus. These bacteria are in the environment and get into the body through breaks in the skin.
The spores can get into the body through broken skin, usually through injuries from contaminated objects. Certain breaks in the skin are more likely to get infected with tetanus bacteria. These include:
- Wounds contaminated with dirt, poop (feces), or spit (saliva)
- Wounds caused by an object puncturing the skin (puncture wounds), like a nail or needle
- Crush injuries
- Injuries with dead tissue
Rarely, tetanus has also been linked to breaks in the skin caused by:
- Clean superficial wounds (when only the topmost layer of skin is scraped off)
- Surgical procedures
- Insect bites
- Dental infections
- Compound fractures (a break in the bone where it is exposed)
- Chronic sores and infections
- Intravenous (IV) drug use
- Intramuscular injections (shots given in a muscle)
The incubation period — time from exposure to illness — is usually between 3 and 21 days (average 10 days), although it may range from one day to several months, depending on the kind of wound. Most cases occur within 14 days. In general, shorter incubation periods are seen with more heavily contaminated wounds, more serious disease, and a worse outcome (prognosis).