Spores of tetanus bacteria exist throughout nature in areas like soil, dust, and manure. They typically enter the body through a break in your skin, such as burn, cut, or wound (including puncture wounds). Once inside your body, the spores develop into bacteria. Tetanus bacteria get stronger in areas of the body with little oxygen. A deep, narrow wound, like a puncture from a dirty nail, can cause a greater possibility of tetanus. It can take anywhere from one day to months for tetanus to develop once bacteria enter your body. According to the CDC, most cases develop within 14 days.