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What Is the Polio Virus? Symptoms, Vaccines and Treatments

US News & World Report - Health 10/3/2022 Vanessa Caceres

Although you don’t hear much about polio nowadays, keeping the virus under control remains a top priority for infectious disease experts around the world.

Polio is an infectious disease that’s formally called poliovirus. It’s been around since ancient times, with some evidence of polio depicted in Egyptian tomb paintings.

Polio spreads from person to person, and most commonly from contact with the feces of an infected person, which can happen with poor hand-washing. Less commonly, polio spreads through contact with droplets caused by a sneeze or cough. It also can be present in food and water in unsanitary conditions, says Dr. Brenda Anosike, a pediatric infectious disease specialist at the Children’s Hospital at Montefiore in Bronx.

At its worst, polio can cause paralysis or death. Although polio can happen at any age, it's more common among young children due to poor hand-washing hygiene.

The History of Polio

By the 1940s, polio outbreaks happened more frequently in the U.S. and affected 35,000 people annually. The virus seemed to spread more easily in the summer, which led parents to feel afraid about letting their children play with others. The largest number of children affected by polio occurred in 1952, with more than 57,000 cases. Some people with polio required an iron lung, a large, life-saving respirator, to help them breathe.

A year later, scientist Jonas Salk developed a polio vaccine and injected himself, his wife and their three sons with the vaccine. Once the vaccine was proven successful, a massive effort to vaccinate began in 1955.

“Mothers brought their children and stood in line for the longest period of time to take advantage of it. We were given buttons to pin onto a shirt to say you were a ‘Polio Pioneer,’” says Dr. William Schaffner, professor of preventive medicine in the Department of Health Policy, and professor of medicine in the Division of Infectious Diseases at Vanderbilt University Medical Center in Nashville.

“Many Americans remember life pre- and post- the Salk vaccine. It was a life-changing event,” says Dr. Aaron Glatt, chairman of the Department of Medicine and chief of infectious diseases and hospital epidemiologist at Mount Sinai South Nassau in Oceanside.

Because of the success of vaccines, the naturally occurring form of the virus was considered eradicated in the U.S. by 1979.

However, this earlier form of the polio vaccine was a live virus and given orally, Schaffner says. In very rare cases, that oral form mutated in the gastrointestinal tract, attacked the nervous system and led to polio-associated paralysis. Because of this problem, health experts switched to a killed, injected form of the vaccine.

Since 2000, the U.S. exclusively uses the injected, inactive polio vaccine. Some countries still use the oral form of the polio vaccine as it’s easy to give, says Dr. Sharon Nachman, chief of the Division of Pediatric Infectious Diseases at Stony Brook Children’s Hospital in Stony Brook.

In 0.09 to 25 of a million vaccines given orally, the polio vaccine can revert and attack the nervous system or be passed to others.

The only two countries where naturally occurring polio remains are Afghanistan and Pakistan, Glatt says. This is due to geographical and political challenges there.

Polio Symptoms

In the majority of people, polio has no symptoms. However, it’s possible to spread the virus right before symptoms emerge and up to two weeks after. It’s possible to spread polio even if you have it without any symptoms. The virus lives in the throat and intestines, Anosike says.

In about 25% of those will polio, the symptoms can easily be mistaken for the flu:

Usually, these polio symptoms will go away on their own in a couple of days.

In a smaller percentage of people with polio, more serious effects develop, including:

  • Paralysis or weakness in the arms and legs. This happens in about 1 in 200 to 1 in 2,000 people with polio. Paralysis can affect the muscles used to breathe, and that’s what leads to death in 2 to 10 of every 100 people with paralysis from polio, the CDC reports. People who are paralyzed have a form of polio called poliomyelitis.
  • Meningitis, which is an infection that occurs in the covering for the spinal cord and brain. This happens in an estimated 1 to 5 of every 100 people with polio.

If you've had polio, post-polio syndrome can happen decades later. Symptoms of post-polio syndrome include:

  • New muscle pain.
  • Paralysis.
  • Weakness.

Diagnosing Polio

Health providers can diagnose polio with a:

  • Physical exam.
  • Medical history.
  • Samples of blood, urine, spinal fluid, stool and throat that are tested. Most commonly, polio is diagnosed via a stool sample.
  • Magnetic resonance imaging that looks at the spinal cord for any damage.

Polio Treatment and Prevention

There's no treatment for polio, but health providers can help control any pain or symptoms that arise from the virus, Anosike says. For instance, physical therapy or occupational therapy may help with arm or leg weakness. A hospital can provide fluids or breathing assistance.

Because there is no formal treatment, vaccines are the preventive step to keep polio at bay. The Centers for Disease Control and Prevention recommends that children get four polio vaccines at the following ages:

  • 2 months.
  • 4 months.
  • 6 to 18 months.
  • 4 to 6 years.

The most typical side effect from the vaccine is arm soreness. In rare cases, a person may have an allergy to the vaccine’s ingredients.

Three doses of the polio vaccine provide 99% protection against the virus, the CDC reports. However, four doses are what's formally recommended for children.

Most adults can assume they received their polio vaccines as a child. Yet there are a few circumstances where a booster dose or a complete series of polio vaccines may be needed:

  • If you’re completely vaccinated for polio but traveling to a high-risk country, then you can receive a booster dose that will last the rest of your lifetime. You may also decide to get a booster if you’re a healthcare worker who may come into contact with the polio virus.
  • If you’re incompletely vaccinated for polio, you should get whatever remaining doses you didn’t get before.
  • If you’re unvaccinated for polio, the CDC recommends a series of three shots: the first dose at any time, the second dose a month or two later, and the third dose six months to a year after the second dose.

In the U.S., 92.5% of children who are two years old have received three doses of the polio vaccine, according to the CDC. Yet that percentage can vary a lot by community. There are some communities that are more vaccine-skeptical where the polio vaccination rate – or any type of vaccine rate – could be much lower, Schaffner says. The COVID pandemic affected vaccination rates overall, Glatt says. That happened due to interruptions with routine health appointments.

Concerns and misinformation about vaccines often spread and can influence vaccination rates, Nachman says. She sometimes has parents who wonder if a polio vaccine is needed if the virus has been eradicated in the U.S. “(Your child) needs the vaccine because someday they are going to travel,” she explains. “Viruses don’t know borders.” Polio is rarely discussed nowadays because vaccinations continue.

In addition to vaccines, good hand-washing can help prevent many types of illnesses, Anosike says.

A More Recent Polio Case

In July 2022, a case of polio was found in an unvaccinated adult male in Rockland County, New York. That person was paralyzed in the legs by the virus.

An analysis of wastewater in the weeks after the case was identified found that polio was circulating in Rockland County and a handful of surrounding counties.

The affected individual in Rockland County likely contracted the virus from exposure to a strain of polio. The strain that was found is the same strain of the weakened virus used in an oral form of the vaccine.

A person who received this type of oral vaccine outside of the U.S. may have been shedding the virus, which can mutate as it continues to shed and eventually reach a strain that can then cause disease in someone not vaccinated against polio.

The polio vaccination rate in Rockland County is a little over 60% compared with a New York statewide average of 78.86% by age 2, according to the New York State Department of Health. The lower vaccination rate in Rockland County is associated with beliefs about vaccines held by some religious groups in that area.

“For every one person who has polio disease, there are hundreds who are infected but undetected,” Anosike says. “This is a very real public health threat as there are concerns for an outbreak of a disease that was once well contained.”

However, that threat is for those who are unvaccinated. “People who are vaccinated don’t need to worry about it. If you are unvaccinated, there’s a risk,” Glatt says.

Copyright 2022 U.S. News & World Report

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