Why is it so dangerous to step on a rusty nail? | Louise Thwaites

0:05This is TED Health, a podcast from the TED Audio Collective. I'm your host, Dr. Shoshana Ungerleiter. Have you ever heard the phrase, don't worry, it's just a scratch? Well, that small cut might carry more than you expect. In this TEDx lesson, Louise Thwaites uncovers the surprising history and science behind tetanus, an infection that doesn't spread from person to person, but through something as simple as a scrape. From ancient shipmasters to modern medical breakthroughs, this talk sheds light on a bacterial threat that's lingered across centuries of human history. You'll rethink that rusty nail or garden shovel and realize why vaccines are more important than ever.

0:47But before we dive in, a quick break to hear from our sponsors.

1:03And now, Louise Thwaites for TED-Ed.

1:10In the 5th century, Greek physician Hippocrates, creator of the Hippocratic Oath, was sailing with a very ill shipmaster. The captain was suffering a nasty infection that caused his jaws to press together, his teeth to lock up, and the muscles in his neck and spine to spasm. Hippocrates dutifully recorded these symptoms, but he was unable to treat the mysterious disease. And six days later, the shipmaster succumbed to his illness. Today, we know this account to be one of the first recorded cases of tetanus. And thankfully, modern physicians are much more prepared to handle this peculiar infection.

1:47Unlike other common bacterial infections like tuberculosis and strep throat, tetanus doesn't pass from person to person. Instead, the offending bacterium, known as Clostridium tetany, infects the body through cuts and abrasions. These infection sites are why tetanus is so strongly associated with rusty nails and scrap metal, which can cause such wounds. But the condition's connection to rust is actually much less direct. Clostridium tetany bacteria are often found in soil, manure, and dead leaves, where they can survive for years in the form of spores, even amidst extreme heat and dryness. These piles of organic material can sit undisturbed for long periods, potentially concealing old metal, which rusts over time.

2:32So if someone does blunder into this environment and cuts themselves, it would likely increase their odds of infection, especially since rusty metal can create jagged wounds with lots of deoxygenated dead tissue for them to latch onto. Once in the body, the spores begin to germinate. This process releases several toxins, including deadly tetanus toxin. Nerve endings soak up this toxin, drawing it into the brain and spinal cord, where it wreaks havoc on interneurons. Typically, these work alongside motor neurons to regulate our muscle actions, from endeavors as complex as kicking a ball to those as simple as breathing.

3:09But by blocking neurotransmitters released by interneurons, tetanus toxin causes uncontrollable muscle contractions and spasms. Typically, within 7 to 10 days of infection, patients begin experiencing general aches, trouble swallowing, and lockjaw. The head and neck tend to show symptoms first. But as the toxin spreads, stronger muscle groups become more rigid, leading to a frightening arching of the back. Left untreated, these spasms become more extreme, eventually seizing the muscles in the windpipe and chest, leading patients to suffocate within 72 hours of symptoms appearing. Without treatment, tetanus has an extremely low rate of survival.

3:50But fortunately, medical professionals have developed a robust plan to handle a tetanus diagnosis. First, doctors clean the infected wound and administer antibiotics, killing the bacteria and preventing further toxin production. Then, they inject antitoxin to neutralize any tetanus toxin still in the body that has yet to enter the central nervous system. Finally, patients begin a several-week period of supportive care, which can include muscle relaxants to stop spasms and ventilators to prevent suffocation. In the days of Hippocrates, the only course of treatment was to wait and hope. But now we know the best time to tackle Clostridium tetany is before an infection even takes place.

4:36Tetanus vaccines, originally developed in the early 1920s, are crucial to preventing tetanus and stopping its spread. Experts recommend a series of shots and boosters beginning at two months old and ending around age 12. Yet over 20 ,000 infants still die of tetanus every year, mostly in low - and middle-income countries where vaccine access is limited, including South Asia and Sub-Saharan Africa. And newborn babies are especially at risk if their mothers are unvaccinated, as Clostridium tetany can infect a newborn's umbilical stump, though vaccinating mothers during pregnancy can help with this problem.

5:13The fact is, tetanus remains a significant threat to human health. So people should get vaccinated and take measures to prevent infection after cutting themselves, whether it's on a rusty nail or a 2 ,400-year-old ship anchor.

5:35That was Louise Thwaites for TED-Ed. And that's it for today. TED Health is part of the TED Audio Collective. This episode was produced by me, Shoshana Ungerleiter, and Constanza Gallardo, edited by Alejandra Salazar, and fact-checked by Vanessa Garcia-Woodworth. Special thanks to Maria Lages, Farah DeGrange, Daniela Balarezzo, and Roxanne High Lash. If you enjoyed today's episode, rate and review the show on your favorite platform. It helps other people find us. And I'd really love to hear your feedback. Send me a DM at ShoshanaMD on Instagram. I'm Dr. Shoshana Ungerleiter, and thanks for listening.

6:22Thank you.