Mental Floss

9 Essential Facts About Polio

Jennifer Billock
Wellcome polio vaccine dropped on to sugar lump for child patient.
Wellcome polio vaccine dropped on to sugar lump for child patient. / Wellcome Collection // CC BY 4.0

We’re still in the midst of the COVID-19 pandemic, monkeypox is spreading fast, and our old nemesis polio decides to pop its head out of the New York City sewer system (and other wastewater facilities nearby) to say hello. That’s right: polio is back in the U.S.

It’s an alarming development, because we haven’t seen cases originating in the United States for more than 30 years. But we have options: You can protect yourself with vaccines and knowledge. So go check those medical records to see if you’re vaxxed, and meanwhile, learn more about the virus with these nine facts.

1. The poliovirus affects the nervous system and spinal cord.

Polio is a fast-moving disease. The polio virus can enter your system, either through contact with water contaminated by infected feces or, more rarely, through infected sneeze or cough droplets. It attacks the nerves’ insulating layer of protein and fats (called myelin) and prevents the nerves from sending and receiving signals. Once the inflammation reaches your spinal cord and nervous system, you face the risk of paralysis in your arms and legs within hours. The paralysis is permanent and can impair your breathing muscles—people affected in this way often ended up in iron lungs. The virus can even be fatal; if you had polio but recovered, serious symptoms can reoccur decades later.

2. The poliovirus can attack anyone.

You may think of polio as a children’s disease, since it mainly affects kids under 5 years old today. But Franklin D. Roosevelt contracted the virus when he was 39. The virus can affect anyone, regardless of age.

3. Infections begin with flu-like symptoms.

At first, polio may seem like a typical flu, with people experiencing a sore throat, fever, fatigue, nausea, headache, and abdominal pain. If the disease progresses, you’ll start to notice a pins-and-needles feeling in your legs, weakness or paralysis, and possible meningitis (inflammation of the fluids and tissues protecting the brain and spinal cord, often causing headaches and a stiff neck).

4. Polio was once endemic.

The first major outbreak of polio in the United States occurred in 1894 in Rutland County, Vermont. It paralyzed 132 people and resulted in 18 deaths, and physicians were unsure of what had caused it. It wasn’t until 1905 that a Swedish physician, Ivar Wickman, published a paper suggesting the disease was contagious. In 1908, the virus itself was identified. It quickly became endemic in the United States, causing an annual panic in summertime, when children and adults were more likely to be bathing in not-so-clean lakes, rivers, and public pools. Outbreaks increased in the 1940s, with more than 34,000 people annually becoming disabled from the virus and thousands dying. One of the worst outbreaks occurred in New England in 1955.

5. Vaccines eradicated the disease from North and South America.

Researcher Jonas Salk, with funding from the National Foundation for Infantile Paralysis (now the March of Dimes), developed an injectable vaccine using the killed poliovirus. He tested it on himself and his family, and the positive results prompted a massive randomized trial of the vaccine in 1.3 million kids in the U.S., Canada, and Finland in 1954. At that time, 58,000 cases of polio occurred annually. After Salk’s vaccine was widely administered, an average 161 cases appeared each year. In 1963, Albert Sabin’s oral polio vaccine—which used an attenuated (weakened but not dead) virus—was approved in the United States. Physicians administered it as a few drops of medicine on a sugar cube, and its convenience and efficacy led it to become the global vaccine of choice until 2000. Thanks to these two vaccines, the U.S. eliminated polio in 1979, and the whole Western Hemisphere eradicated it by 1991.

6. Only a handful of countries are still battling polio.

Polio has never been fully eradicated from the world. Afghanistan and Pakistan still have endemic spread, and cases among travelers have emerged periodically. In July 2022, an unvaccinated man in Rockland County, New York, developed paralysis from a polio infection. He had not traveled out of the country, so officials believe he contracted it from someone who had been in a region that still used the oral vaccine; people receiving the oral vaccine can shed the virus in their feces and cause infections. It was the first case of polio in the U.S. since 2013. Hopes that it would be a one-off incident were dashed when traces of poliovirus, genetically related to that case, were found in wastewater samples from Rockland and neighboring Orange County and in the New York City sewage system.

7. You’re not likely to become seriously ill if you catch the poliovirus—but it’s possible.

Today, according to the CDC, most people who have polio (about 72 percent) won’t have any symptoms. A quarter of infected people will just feel like they have a nasty cold or flu for two to five days, and then it will resolve. But for every 100 cases, one to five people will have serious symptoms like meningitis, and one in 200 or more cases will have paralysis, depending on the type of poliovirus involved.

8. There’s no cure for polio. 

Throughout the virus’s history, scientists have been unable to find a cure for polio. But many countries have been able to eradicate it by community vaccination, which prevents the virus from spreading until it eventually dies out.

9. Vaccination is the best way to protect yourself from polio.

The inactivated polio vaccine, introduced in 1955, is extremely safe and 90 percent effective against paralytic polio. It’s the only one the U.S. has administered since 2000. Every state requires a polio vaccine for children to go into childcare or school, so it’s very likely you’re already vaccinated, and have been since your first round of vaccinations when you were a toddler. If, for some reason, you weren’t vaccinated as a child, you can still get the three-dose polio vaccine as an adult. And if you’re at a higher risk of catching the virus (if you’re a healthcare worker or traveling somewhere with high polio rates, for example), then you can obtain a booster shot for added protection.