New York City health officials announced last week that they detected polio in wastewater, suggesting that the dangerous virus is silently spreading within the nation’s most populous metropolis. The spotting happened about a month after nearby Rockland County became the first American locale in nearly a decade to report a symptomatic case of polio. The virus is also cruising through sewage in Orange County, which sits next to Rockland in the Hudson Valley.

For decades, the country hasn’t had to worry about community transmission of polio. Thanks to childhood vaccination, most people in the U.S. have been protected for 70 years, and homegrown outbreaks were eliminated from both North and South America by 1994.

It would be easy to fret now — especially with the news coming on the heels of more than two years of COVID-19 and a summer of monkeypox. But a slew of health researchers told Gothamist that it isn’t time to panic. Only a single symptomatic case has been identified in New York so far. But a new vaccination push is warranted, given that some cracks have emerged in our collective defenses.

“If we start getting three or four or five random cases in New York City, then I would definitely be looking for my vaccine schedule and make sure I've been vaccinated,” said Dr. David Buchholz, a pediatrician and the senior founding medical director for primary care at Columbia University Irving Medical Center.

Polio is almost exclusively a threat to the unvaccinated — and based on current immunization rates, many neighborhoods in New York City and counties statewide are below the levels needed to keep the virus from thriving among youngsters, the most vulnerable age group.

The threat was more severe in the 1940s and 1950s, when the virus killed thousands of Americans each year and paralyzed scores more. The afflicted were mostly children, but included adults like President Franklin D. Roosevelt. Back then, the polio virus, which primarily spreads via fecal matter, contaminated water in swimming pools and even drinking fountains. Many of those threats are long gone in high-income nations due to vaccination and public infrastructure such as water treatment.

“Are we going to see the numbers we saw in the '50s or in the '40s?” asked Dr. Perry Halkitis, dean of the Rutgers School of Public Health. “Unlikely.”

But some technological gaps remain in understanding our collective public health. Most New Yorkers, for example, will have an easier time checking their order history on Uber Eats than finding their childhood vaccination records.

“Over the course of your lifetime, particularly if we're thinking about immunizations you might have received as a child, you've moved around to a lot of different organizations,” said Dr. Julia Adler-Milstein, a professor of medicine at the University of California San Francisco who directs its Center for Clinical Informatics and Improvement Research. “That means that your history is fragmented in all those different places that you've been.”

It’s also unclear how many New York residents might be carrying polio right now because wastewater surveillance cannot reveal such information.

Right now, the methods can simply tell the presence or absence of polio, stated Syracuse University epidemiologist Dr. David Larsen, who helps manage the New York state wastewater surveillance network, via email. “There needs to be further development to estimate trends in transmission.”

So for any New Yorker who can’t find their vaccine documents, who has a young kid at home who hasn’t completed their vaccine schedule, or who simply wants to know if they might be at risk if an epidemic emerges, here’s a guide to facing a polio outbreak in 2022 — just in case.

What happens if you catch polio

Do I need to worry about a polio outbreak?

Only if you lack immunity to polio. This situation would mainly apply to a child or adult whose parent or caregiver hasn’t followed the state-required vaccine schedule for school attendance.

If you’re a senior citizen, it could mean you, too — given that the human immune system wears away in old age.

I heard most polio cases don’t have symptoms. How likely is someone who gets it to become seriously ill?

Ninety-nine percent of people who have completed a full course of polio vaccines will be fully immune to the virus, meaning they can’t physically develop disease from it for decades. The vaccine is one of the most effective ever developed.

About 70% of people infected with polio experience no symptoms at all, according to the Centers for Disease Control and Prevention and the New York City health department. Similar to COVID-19, they end up being asymptomatic carriers of the virus, which helps it move through a community. New York’s current outbreak is a great example of this phenomenon. Wastewater surveillance suggests that the virus is somewhere in Rockland County, Orange County, and New York City — but only one case has been identified and reported statewide so far.

Around a quarter — 24% — of infected people develop mild polio, which will feel like the flu or a mild case of COVID-19. They can expect a sore throat, fever, tiredness, and perhaps some nausea that lasts less than a week.

Karen Oaks of Detroit, a polio patient, inside an "iron lung," January 1946. Iron lungs are still used today to help paralysis patients breathe.

Karen Oaks of Detroit, a polio patient, inside an "iron lung," January 1946. Iron lungs are still used today to help paralysis patients breathe.

Karen Oaks of Detroit, a polio patient, inside an "iron lung," January 1946. Iron lungs are still used today to help paralysis patients breathe.
Bettmann via Getty Images

About 4% of infected people will develop a brain infection called aseptic meningitis. They can expect to recover, according to the CDC, and typically won’t become paralyzed. But a person will feel stiff in the neck, back, and legs. It can be painful and can also lead to vomiting.

Historically, about one in 200 infected children — 0.5% — have developed paralysis within three weeks of catching polio. (These odds drop to about one in 1,900 for the specific strain of the virus that’s circulating in New York, polio type 2, based on an analysis from the University of Pennsylvania.)

The worrying part is that the condition might develop over time. About 25% to 40% of these childhood cases showed worsening paralysis about 15 to 40 years after the fact, according to the CDC.

The federal health agency states that the case-fatality rate — or the proportion of people who die with each known infection — also increases with age. Two to 5% of children who develop polio will die, but among adults, those odds increase to 15% to 30%.

How polio spreads

How do people typically catch polio?

Polio is an enteric virus, meaning it primarily exists in the gut or intestines. For this reason, it usually spreads when fecal matter gets into people’s mouths.

But the virus can also live in the nose and throat for one to two weeks, according to the CDC, allowing it to spread via sneezes and coughs. The CDC says infected people with and without symptoms can spread the disease.

That’s not me, man. I don’t get poop in my mouth.

Unfortunately, you probably do.

A 2018 study of 73 families found fecal germs on 62% of individuals’ hands. A 2009 study of hundreds of U.K. bus commuters found that more than a quarter had butt bacteria on their hands.

People touch their eyes, mouths, and faces about 50 times per hour.

There were old stories of people contracting it after swimming in lakes and pools. Is that a real risk?

It’s not really a risk for pools anymore because chlorination neutralizes the polio virus.

Halkitis from Rutgers said the main concern today would be small stagnant bodies of water.

“The most problematic bodies of water are those where there's no outlets, where there's no movement, where there's no chlorination — where it's just like sitting there,” he said.

What about ocean water? Didn’t NYC just close some beaches due to germs?

It’s highly unlikely. Lab studies show that the polio virus can physically survive in seawater for hundreds of days — but only if the water is cold (about 39.2 degrees Fahrenheit). Raise the temperature to a more normal level of 77 degrees Fahrenheit, and the virus only survives 25 days.

The bigger impediment is the sun. Sunlight is also shown to inactivate more than 90% of polio viruses in marine water after 24 hours.

Also, the recent beach closure was due to bacteria, rather than viruses.

Is there anything else I can do to reduce my chances of getting it (handwashing, etc.)

Yes, health experts recommend handwashing to prevent the spread of polio, given the fecal matter thing. Masks will also help stop those sneezes and coughs from spreading the virus.

Polio vaccination: the basics

Are there medicines that can cure polio once you get it?

Unfortunately, no. Because the polio vaccine is 99% effective, there’s been no incentive to develop a therapeutic drug for the virus.

How many people need to be vaccinated to achieve herd immunity?

Herd immunity can only be achieved with the oral version of the polio vaccine, which health providers no longer give in the U.S. (More on that later). But in some places, the current vaccination rates wouldn’t cut it for that purpose anyway — and that may speak to a rise in hesitancy.

The herd immunity threshold is the point at which so many people in a community are immune that a germ cannot mathematically spread within it. For polio, health experts estimate that 80% to 85% of a population needs to be immune for herd immunity to kick in.

But a community, in the context of where a virus moves, can refer to a lot of different settings: a school, a neighborhood, a borough, or a city.

A map of polio vaccination rates among children aged 6 months to 9 years. Vaccination rates vary widely and are lowest in north Brooklyn.

Polio vaccination rates vary widely between neighborhoods. They're lowest in Williamsburg, Brooklyn.

Polio vaccination rates vary widely between neighborhoods. They're lowest in Williamsburg, Brooklyn.

New York City health officials, for example, stated on Friday that the citywide polio vaccination is 86% on average for kids under 5.

But the rate drops below 80% for several neighborhoods across the five boroughs. Parts of Brooklyn, Staten Island, and Queens are below 70%. Williamsburg is at 56% fully vaccinated for these youngsters.

Similar low rates in Rockland County may explain why a paralytic case popped up there all of a sudden.

Do I need to be fully vaccinated against polio?

Children and adults given a full set of shots are essentially guaranteed to never have any issues with the virus given that 99% of recipients become immune.

What if my infant is too young for the polio vaccine?

In the U.S., kids get four doses of the inactivated polio vaccine to be considered fully vaccinated. One dose is recommended at each of the following ages:

  • 2 months old
  • 4 months old
  • 6 through 18 months old
  • 4 through 6 years old

Buchholz from Columbia advises parents to prevent contact between newborns and strangers — until they start their childhood vaccines.

Kids line up to get their polio vaccines at the Woodbury Avenue School in Huntington, New York on April 27, 1954.

Kids line up to get their polio vaccines at the Woodbury Avenue School in Huntington, New York on April 27, 1954.

Kids line up to get their polio vaccines at the Woodbury Avenue School in Huntington, New York on April 27, 1954.
Walter del Toro/Newsday RM via Getty Images

“Particularly for the first six to eight weeks of life, when their immune systems really are not adult-like, they need to be protected as if they're immune compromised,” Buchholz said. He says limit household visitors if you can and make sure people wash their hands before touching your newborn.

The first dose of polio vaccine is thought to protect 80% of kids who receive it. Two doses bump up the effectiveness to 90%, while three doses get people to 99%.

Do I need a booster shot?

I heard the U.K. is giving booster shots to kids?

The U.K. has a different vaccine schedule. The U.S. gives a fourth (booster) shot in preschool and kindergarten to help lock in protection for decades.

The Brits give the booster shot to adolescents, but given the recent detection of polio in sewage, their health officials opened up additional doses to kids ages 1 to 9.

I’m an adult. Do I need a booster shot?

The answer is most likely no, but it depends on how long it’s been since your vaccines.

Polio immunity is potentially lifelong for most people, but let’s give a breakdown.

Antibodies are our immune system’s early line of defense against intruders and tend to keep infections from starting in the first place. Studies have found antibodies against polio still present in people’s bodies about 20 years after vaccination.

We assume, for the most part, [that] people are fully protected based on the vaccinations they got as a child.

Dr. Michael Merson, a professor of global health at NYU.

“We assume, for the most part, [that] people are fully protected based on the vaccinations they got as a child,” said Dr. Michael Merson, a professor of global health at NYU.

T-cells, another part of the immune system to ward off severe disease with polio, also appear to last for decades.

But society is starting to move into uncharted territory with the duration of our polio shields. Immune systems weaken in old age. A 2005 study found Dutch people born between 1925 and 1945 might be able to catch and excrete polio virus after exposure.

If I'm not vaccinated, is it easy to get vaccinated? How much will it cost?

Yes, adult polio vaccination is sometimes recommended for travelers heading to places where the virus is common.

If you’re in the U.S. and want to take the polio vaccine on its own, then you’ll be using a brand called IPOL, which is commonly known as enhanced potency inactivated polio vaccine. It’s list price is $38, which may or may not be covered by your insurance if you’re an adult.

Required pediatric vaccines tend to be free or low cost thanks to the federal Vaccines for Children Program, which is managed by the CDC. Some pediatric brands combine the polio vaccine with other shots for diseases such as tetanus or whooping cough, so a kid can get more done with a single dose.

Finding your old records

I’m in my 20s. Can I easily find my vaccination record?

Yes, the youth are in luck. Starting in the early 1990s, the U.S. began systematically documenting these childhood vaccine drives in what are called Immunization Information Systems.

Congress and the CDC gave funds to states to set up registries, where the vaccine records could be stored — and over time, these records moved online.

Each kid is typically given an IIS number, so they can put in a request with their state health departments.

Note: This is not a federally run system, so don’t contact the CDC for these records.

What if I’m older? And what’s the easiest way to access them?

This could be tricky. If your parent didn't hang on to your immunization records you're likely counting on the record-keeping practices of your old doctor, or the state where you grew up, and those can be spotty.

“As result of the COVID-19 response, a lot more adults are now being enrolled into the immunization information systems,” said Dr. L.J. Tan, chief strategy officer for the nonprofit Immunize (formerly the Immunization Action Coalition). “But, adults are nowhere as complete with those records.”

The easiest way to access your state’s IIS records is via your health care provider. They can typically just log directly into the system to verify your identity and download what’s there.

Adults who are seeking their polio immunization history can reach out to their healthcare provider to see if they have that information available.

Monica Pomeroy, New York State Department of Health

“Adults who are seeking their polio immunization history can reach out to their health care provider to see if they have that information available,” said Monica Pomeroy, a public information officer with the New York State Department of Health. “However, New York State Immunization Information System was established in 2008, so data may not be available prior to 2008.

New York City has its own separate system called the Citywide Immunization Registry.

Or you could head to your attic and start opening boxes of your elementary school art projects to see if anyone kept your childhood medical records.

Immunize has a tip sheet that also recommends contacting an old school or employer for the records. Typically, schools and daycares must receive written consent from parents or an eligible student to give out vaccine documents.

What if I don’t have a health care provider?

Here’s a national contact list, and the IIS information for the tristate area. Right now, IIS records can’t be transferred across state lines, so people need to call their home states for info.

You’ll typically need to provide identification with the requests.

Call: 860-509-7929
Web: Connecticut WebIZ

New Jersey
Call: 609-826-4860
Helpdesk: Submit a ticket
Request an Immunization Record Request: NJIIS

New York State (except New York City)
Call: 518-473-4437
Web: New York State Immunization Information System

New York City
Call: 347-396-2400
Web: New York Citywide Immunization Registry
Immunization Records:

If I can't find out if I am vaccinated, then what are my options?

If you strike out with your health care provider, your home state’s immunization repository and your attic, your doctor can prescribe a full course of vaccine or a booster shot.

“If they really aren't sure and they are concerned, [there’s] certainly no harm in getting a booster,” said Merson from NYU. “Or if they really don't believe they were vaccinated, [there’s] no harm in getting a full series of vaccinations: three doses.”

It’s hard to believe that finding vaccine records is this difficult.

Too true. Adler-Milstein from UCSF said it would make more sense for there to be a federal system, where kids are given a national ID number for their vaccine records. But it would be hard to unify all the state systems.

“Different states have built their immunization registry systems differently. There's no standard that exists,” she said. “A national patient identifier would really help reduce some of the friction to a better national picture of immunization reporting.”

Vaccine-derived polio virus

Health officials are telling people to get immunized, but wasn’t this outbreak caused by a vaccine?

Yes, let’s address the elephant in the room: The polio circulating in New York — which is genetically tied to viruses detected in sewage in the U.K. and Israel — started with a vaccine. It’s no surprise. Researchers have known such a thing is possible for decades.

How could this happen?

These days, two versions of the polio vaccine are used worldwide: the oral polio vaccine and inactivated polio vaccine.

The oral vaccine is made by taking a live virus and weakening it. Inject this weakened virus into the overwhelming majority of people, and their bodies will mount a safe immune response. OPV is also technically stronger because it partially sets up shop in the gut.

A health worker administers oral polio vaccine drops to a child during a door-to-door campaign in Karachi, Pakistan, June 27, 2022.

A health worker administers oral polio vaccine drops to a child during a door-to-door campaign in Karachi, Pakistan, June 27, 2022.

A health worker administers oral polio vaccine drops to a child during a door-to-door campaign in Karachi, Pakistan, June 27, 2022.
Asif HASSAN / AFP via Getty Images

Yet on very rare occasions, the attenuated virus in the oral polio vaccine mutates — as all viable germs and organisms can. By doing so, it regains its full potency and can cause disease.

This reversion problem typically occurs in immunocompromised people (where viruses often find niches to thrive) or in places with low vaccination rates (which give vaccine-derived polio a chance to spread).

Vaccine-associated paralytic polio is still incredibly rare. It occurs about once in every 2 million to 3 million recipients of oral polio vaccine. Without the vaccine, your chances of getting paralytic polio are more like one in 200.

Also, this problem doesn’t occur with the inactivated polio vaccine. It contains killed versions of the virus, as its name suggests, so it can’t mutate and revert back to being live.

Well, why don’t countries stop using OPV?

The U.S. did — it stopped using the oral vaccine in 2000. Most high-income and middle-income countries have done the same.

The oral polio vaccine is still used elsewhere because it’s much cheaper (12 to 18 cents) than inactivated polio vaccine ($1.00 to $3.28).

This price difference seems small, but it adds up quickly. A 2021 study, led in part by researchers at Yale, estimated that 348.7 million doses of inactivated vaccine would be needed annually to maintain immunization drives. Do some quick math with the maximum prices above, and you’ll find a global savings of $1 billion by using the oral polio vaccine versus the inactivated version.

And that price point doesn’t account for labor. The oral vaccine is easier to administer given that it doesn’t require needles, shots, or nurses. (Ask your parents and grandparents about taking sugar cube polio vaccines.)

An unidentified child takes a dose of the Sabin vaccine for polio immunization, administered on a sugar cube, in 1967.

An unidentified child takes a dose of the Sabin vaccine for polio immunization, administered on a sugar cube, in 1967

An unidentified child takes a dose of the Sabin vaccine for polio immunization, administered on a sugar cube, in 1967
US Public Health Service/PhotoQuest/Getty Images

History and research have shown that the world would not be on the verge of eradicating polio without the oral vaccine. It’s actually better at stopping spread between people.

But given the problem of reversion, the World Health Organization, UNICEF, and other immunization alliances are phasing out the oral polio vaccine.

The switch started in 2016, when the formula for oral polio vaccine was switched. It typically contains three different strains of polio virus. But one of the strains — polio type 2 — was linked to 90% of vaccine-associated paralysis cases, so it was removed from the formula.

Simultaneously, there’s been a push by countries and foundations to get inactivated polio vaccine into every nation in the world — a feat finally accomplished in 2019.

There’s still a long road to go. Remember: 348 million doses of inactivated polio vaccine are needed annually. In 2020, the drugmakers only made about 80 million to 100 million.

Editor's note: This story was updated to clarify the section on herd immunity.