If you ask most people when polio disappeared from America, they’ll probably point to some grainy black-and-white photo from the 1950s. They imagine the "iron lung" era ended the second Jonas Salk’s vaccine hit the shelves. But history is a lot messier than that. Honestly, the answer to when was the last polio case in the us depends entirely on how you define "case."
Are we talking about the old-school wild virus that used to paralyze thousands of kids every summer? Or are we talking about the strange, modern versions that keep popping up in our wastewater?
The reality is that polio didn't just vanish in 1955. It lingered. It traveled. And as we saw recently in New York, it still knows how to find the gaps in our defenses.
The 1979 Turning Point: The Last of the "Wild" Days
For most medical historians, the "official" end of homegrown polio in the United States happened in 1979. That was the last time the wild poliovirus—the kind that naturally circulates in the environment—was transmitted within U.S. borders.
It wasn't some quiet exit, either. The 1979 outbreak hit Amish communities across several states, including Pennsylvania, Iowa, Wisconsin, and Missouri. Because these communities often had lower vaccination rates, the virus found a foothold. It was a stark reminder: the virus doesn't care about your lifestyle; it only cares if you’re protected.
After those final 1979 cases, the U.S. went into a bit of a "wild-free" era. But that doesn't mean polio disappeared from our soil entirely.
The 1993 Imported Scare
In 1993, the wild virus made a brief, unwelcome return. It didn't start here, though. A traveler brought it into the country. This is what experts call an "imported case." While it didn't trigger a massive national epidemic, it proved that as long as polio exists anywhere in the world, the U.S. is just one plane ride away from a potential outbreak.
The 2022 Wake-Up Call in Rockland County
If you thought polio was ancient history, July 2022 was a massive reality check. A young, unvaccinated adult in Rockland County, New York, was hospitalized with symptoms that doctors hadn't seen in decades: legitimate, classic paralysis.
Testing confirmed it. It was polio.
But this wasn't the "wild" virus from 1979. It was something called vaccine-derived poliovirus type 2 (VDPV2). This sounds confusing, so let's break it down.
- Some countries use an oral polio vaccine (OPV) that contains a weakened, live virus.
- In rare instances, that weakened virus can circulate in under-vaccinated populations and eventually mutate back into a form that causes paralysis.
- This mutated virus then hitches a ride to the U.S. via travel.
What happened next was even more unsettling. Health officials started testing sewage. They found the virus in wastewater in New York City, Orange County, and Sullivan County. Basically, the virus was circulating silently in the community for months. One person got paralyzed, but hundreds of others likely had the virus without even knowing it.
The 2022 Rockland County case is technically the most recent instance of paralytic polio acquired within the United States.
Why the "Last Case" Keeps Changing
When you look at the timeline of when was the last polio case in the us, it feels like a moving target because the science of vaccines changed.
Up until 2000, the U.S. used the oral vaccine (the "Sabin" drops). It was great for stopping outbreaks, but it had a tiny, tiny risk of causing "vaccine-associated paralytic polio" (VAPP). Around 8 to 10 people every year would actually get polio from the vaccine itself.
Because we’d already kicked the wild virus out, that risk became unacceptable. So, in 2000, the U.S. switched exclusively to the Inactivated Polio Vaccine (IPV)—the shot. The shot cannot cause polio. Period.
The Current Landscape (2025-2026)
As we move through 2026, the data from the CDC and public health departments shows a worrying trend. Vaccination rates for kindergartners have been dipping. In the 2024-2025 school year, national polio vaccination coverage dropped to about 92.5%.
That might sound high, but "herd immunity" for polio usually requires about 80% to 90% coverage to keep the virus from spreading. Some states, like Idaho, have seen rates drop much lower, leaving pockets of people vulnerable to the kind of silent transmission we saw in New York.
What Most People Get Wrong About Polio Today
There’s a dangerous myth that polio is "gone." It isn't. It’s "eliminated" in the U.S., but not "eradicated" globally. Only two countries—Pakistan and Afghanistan—still have the original wild poliovirus (Type 1) as an endemic fixture.
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But as long as those reservoirs exist, and as long as vaccine-derived strains are circulating in places like London, Jerusalem, or Montreal, the U.S. remains at risk.
The symptoms are also a bit of a trick. About 75% of people who catch polio have zero symptoms. They feel fine. They go to the grocery store. They go to work. But they are shedding the virus in their stool, and it ends up in the wastewater.
Only about 1 in 200 to 1 in 2,000 people actually end up paralyzed. The New York case in 2022 was just the "tip of the iceberg." For that one paralyzed person, there were likely hundreds of asymptomatic carriers.
How to Protect Yourself and Your Family
The conversation around when was the last polio case in the us usually leads to one question: "Am I still safe?"
If you were vaccinated as a kid in the U.S., you’re likely good for life. The CDC says three doses of the IPV are at least 99% effective against paralysis. However, if you're traveling to a country where polio is still active, or if you live in a community where vaccination rates have tanked, you might need a booster.
Actionable Steps for 2026:
- Check Your Records: Don't guess. Look for your "Yellow Card" or digital health records. If you haven't finished the 4-dose series, get it done.
- The Lifetime Booster: If you are an adult traveler going to "high-risk" areas (parts of Africa, the Middle East, or Asia), the CDC now recommends a one-time lifetime IPV booster.
- Watch the Wastewater: Many local health departments now post wastewater surveillance data online. It’s a great way to see what’s actually moving through your city before it hits the news.
- Understand the "Why": If you hear about a case in 2026, don't panic. Ask if it’s "wild" or "vaccine-derived." It helps you understand the risk. Vaccine-derived cases usually mean there’s a gap in local immunity.
The story of polio in America didn't end with a "The End" title card in 1979. It’s an ongoing battle of surveillance and maintenance. The 2022 New York case was a loud, clear warning that we can't afford to be complacent. Keeping polio in the history books requires staying active in the present.