What to Know About Polio: Vaccines, Symptoms and How It Spreads

A recent case in a New York suburb has reignited concerns over the disease.

An illustration depicts a polio virus particle.
Credit…CDC, via Associated Press

Dani Blum

During the slog of yet another Covid wave, and mounting monkeypox anxieties, health officials in a New York suburb reported a case of polio in July — the first detected in the United States in nearly a decade.

State health officials said that polio was detected in an unvaccinated person in Rockland County, New York, and that the virus had been found in county wastewater samples in June, as well as in wastewater samples in two different locations in Orange County, New York. These occurrences, as well as reports that health officials in Britain had detected evidence of poliovirus in sewage samples in London, have reignited polio concerns.

Here’s what you need to know about the disease.

Polio, also known as poliomyelitis, is a sometimes disabling and life-threatening disease caused by the poliovirus. The disease mainly affects infants and children under 5, but anyone who is unvaccinated can contract it.

There is no cure for polio, but widespread vaccination has proved to be an effective prevention strategy. No cases have originated in the United States since 1979, and before July, there hadn’t been a reported U.S. case since 2013.

During the early 1950s, before vaccines were widely available, polio outbreaks caused more than 15,000 cases of paralysis each year. But that symptom is rare — and many people don’t develop any visible symptoms of the virus at all.

“Most people who get polio will not even know they got polio,” said Dr. Frank Esper, a pediatric infectious diseases specialist at the Cleveland Clinic in Ohio. Seventy-two percent of people who contract it are asymptomatic, according to the Centers for Disease Control and Prevention.

About a quarter of those infected experience flulike symptoms, but “it’s more the stomach flu than a cold flu,” Dr. Esper said. Typically, symptoms like sore throat, fever, fatigue, nausea, headache and stomach pain last for around three to seven days, he said, but people can still spread polio for three or more weeks.

A smaller subset of people who contract polio (less than one in 100, according to the C.D.C.) develop symptoms that affect the brain and spinal cord. Some of those people may experience a tingling sensation in their legs, often described as pins and needles. Others, about one in 25 people, may develop meningitis, which involves swelling of the membranes that cover the brain, spinal cord or both.

The C.D.C. estimates that only one in 200 people with polio experience paralysis or weakness in the arms, legs or both. Paralysis typically occurs on one side of the body, said Dr. Gail Shust, a pediatric infectious disease specialist at NYU Langone Health. In rare cases, polio-related paralysis can be fatal, as the virus may affect muscles that support breathing.

Even after someone recovers from polio, they can develop muscle pain, weakness or paralysis 15 to 40 years later. Children who recover from polio may experience post-polio syndrome as adults, with muscle weakness, fatigue, and joint pain setting in decades after their initial infection. It’s not clear why only some people develop post-polio syndrome, but those who experienced severe polio cases may be more susceptible.

Polio is very contagious. It spreads from person to person — typically, when someone is in contact with the feces of an infected person and then touches their mouth. This is particularly concerning for children under 5, who, Dr. Esper said, may struggle with hand hygiene. “Every adult who has children knows that’s how germs are spread,” he said. Less commonly, polio can be spread when droplets from an infected person sneezing or coughing enter someone’s mouth.

And as with Covid-19, it is possible to spread the virus even if you don’t have symptoms.

The oral polio vaccine, which helped the United States eliminate polio and is not administered in the country any more, contains weakened live poliovirus. In rare cases, the virus can revert to a so-called “vaccine-derived polio,” and can lead to disease, said Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia. Health officials in New York confirmed that the person in Rockland County was exposed to someone who received the oral polio vaccine, which mutated to a pathogenic form of the virus. The oral polio vaccine has not been administered in the United States since 2000. Today, the polio vaccine in the United States is a highly effective shot, which does not contain live virus, unlike the oral vaccine.

There are many countries that still use the oral vaccine. “We’re always at risk of having that vaccine-derived strain come into this country,” Dr. Offit said.

Vaccination is the best way to guard against polio, and the highly effective vaccine is part of a regular childhood immunization schedule in the United States.

“This is the good news about living in the vaccine era,” said Dr. Offit, who grew up during the 1950s and remembered his mother forbidding him from swimming in a public pool for fear of contracting the virus. “You just need to get vaccinated.”

Most U.S. adults do not need to get vaccinated for polio, since they likely were vaccinated as children (who typically receive four doses of the vaccine by age 6). Still, doctors might advise a booster shot for those traveling to an area with high rates of polio, as well as those treating patients or working with poliovirus in a laboratory setting.

“I cannot stress this enough: Vaccine, vaccine, vaccine,” Dr. Shust said. If you have not been vaccinated against polio, or are not sure if you received the vaccine as a child, she recommended talking to your doctor and, if you live, work or attend school in Rockland County, seeking out the vaccine as soon as possible. The shot does not have significant side effects, Dr. Esper said, except for rare cases of allergic reactions, which can occur with any immunization or medication.

And as with Covid-19, proper hand hygiene is also imperative for curbing the spread of polio.

While the re-emergence of polio is concerning, experts said that the average person does not need to change their day-to-day behavior or panic.

“If you’re vaccinated, you don’t have to worry,” Dr. Offit said.

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