You get tetanus when bacterial spores from the environment enter your body through a break in the skin. The bacterium, found naturally in soil, dust, and animal manure, exists as tough spores that can survive in the environment for years. Once inside a wound with the right conditions, those spores activate, multiply, and produce a powerful toxin that attacks the nervous system. Tetanus is not contagious between people.
Where Tetanus Bacteria Live
Tetanus spores are everywhere. They’re common in soil, household dust, and animal feces. These spores are extraordinarily resilient: they resist most disinfectants (including alcohol-based ones), survive extreme temperatures, and can remain viable in soil for many years. Standard cleaning won’t reliably eliminate them from an environment. This widespread presence is why any unvaccinated person with a skin break is potentially at risk, not just people who step on rusty nails.
How Spores Enter the Body
The spores need broken skin to get in. The highest-risk wounds are those contaminated with dirt, feces, or saliva, along with puncture wounds from objects like nails or needles, and injuries involving dead tissue such as burns, crush injuries, and frostbite. These types of wounds are classified as “dirty” or major wounds in clinical terms.
Less obvious entry points include chronic sores, dental infections, insect bites, surgical sites, and injection sites from intravenous drug use. Essentially, any break in the skin can serve as a door, though deep or contaminated wounds carry the greatest risk.
What Happens Inside the Wound
Tetanus spores don’t cause problems on their own. They need low-oxygen conditions to activate, which is why deep puncture wounds and injuries with crushed or dead tissue are particularly dangerous. These wounds create pockets where oxygen can’t reach. In that oxygen-poor environment, the spores germinate into active bacteria and begin producing a toxin.
That toxin travels along nerves to the spinal cord, where it blocks the release of chemicals that normally keep muscles relaxed. Without those calming signals, your muscles receive constant “contract” commands with no off switch. The result is the severe muscle stiffness and spasms that define tetanus, starting most often in the jaw (which is why tetanus is sometimes called lockjaw) and spreading to the neck, trunk, and limbs.
How Quickly Symptoms Appear
The incubation period ranges from 3 to 21 days, with an average of about 8 days. Two factors influence timing. First, the farther the wound is from the brain and spinal cord, the longer the toxin takes to travel there, so a foot wound may produce symptoms later than a facial wound. Second, a shorter incubation period generally signals more severe disease and a higher chance of death.
There’s also a rarer form called cephalic tetanus, which follows head or face wounds and has an incubation period of only 1 to 2 days.
Neonatal Tetanus
Newborns can develop tetanus within the first 28 days of life if the umbilical cord stump is contaminated. This happens when deliveries occur in unsanitary conditions, when the cord is cut with unclean instruments, or when contaminated materials like animal dung or dirt come into contact with the stump. Symptoms typically appear 4 to 14 days after birth, averaging about 7 days. Vaccinating mothers during pregnancy transfers protective antibodies to the baby, which is one of the primary strategies for preventing neonatal tetanus globally.
Who Is Most at Risk
Vaccination status is the single biggest factor determining your risk. CDC surveillance data from 2009 to 2023 shows that no deaths occurred among people who had received three or more vaccine doses. By contrast, unvaccinated individuals had a case-fatality rate of 12.5%.
Age plays a dramatic role in survival. Among adults 18 to 34, the case-fatality rate was just 1.2%. For people 65 to 79, it jumped to 30.8%, and for those 80 and older, it reached 63.3%. This steep increase reflects both weaker immune responses in older adults and the fact that many older people have not kept up with booster shots. Overall, roughly 1 in 10 people who develop tetanus in the United States will die from it.
The Rust Myth
Rust itself doesn’t cause tetanus. The association exists because rusty metal objects are often found outdoors in soil, which is where tetanus spores thrive. A rusty nail in a garden is dangerous because it’s contaminated with soil, not because of the rust. A clean, shiny knife that’s been in contact with dirt or manure carries the same risk. Any wound, from a thorn scratch to an animal bite, can introduce spores if contaminated material gets under the skin.
How Vaccination Prevents Infection
The standard schedule calls for a childhood vaccination series, followed by a booster (Td or Tdap) every 10 years throughout adulthood. Pregnant women are recommended to receive one dose of Tdap during each pregnancy to protect both themselves and their newborns.
If you get a dirty or major wound and it’s been more than five years since your last booster, you’ll likely receive a dose as part of wound management. For clean, minor wounds, the threshold is 10 years. Proper wound care matters too: cleaning the wound thoroughly and removing any dead tissue or foreign material reduces the low-oxygen conditions that spores need to activate.
Because tetanus spores are so widespread and resilient, avoiding exposure entirely isn’t realistic. Vaccination is the only reliable protection, and the data is stark: three or more doses reduced the fatality rate to zero in 15 years of U.S. surveillance.