The re-emergence of what was once considered an eliminated health threat is causing concern to the general public. The poliovirus has recently been discovered in New York, London, and Jerusalem. Out of the active cases, only two involved polio-related paralysis, the more serious effect of the disease. However, with the New York case being the first in the United States in about a decade and more alarming reports coming in, public health specialists and the public are concerned that the virus could have been circulating for months.

According to Walter Orenstein, a professor of infectious diseases at Emory University in Atlanta, Georgia, the new cases could be the "tip of the iceberg." Dr. Yvonne Maldonado of the Stanford School of Medicine confirmed that the case in New York was an unvaccinated male and that there's evidence the virus has been circulating in the city's wastewater.

Upon testing wastewater samples from New York, London and Jerusalem, experts said there's reason to believe the virus has been circulating more widely. According to Nature, the virus found in the three locations could have come from an oral polio vaccine used in countries outside of the U.S. It's not clear how the first case in the Big Apple got the oral vaccine.

What is this highly infectious, preventable, but incurable disease? How can it be prevented? Let's find out:

What is polio?

Also known as poliomyelitis, polio is a disabling and highly-infectious, life-threatening disease caused by the poliovirus, which infects a person's spinal cord and may result in irreversible paralysis in one in 200 infections.

There were only six reported cases in 2021, a 99% reduction from the estimated 350,000 cases of wild poliovirus in 1988. According to the World Health Organization (WHO), among those paralyzed, about 5-10% die due to the virus immobilizing the muscles that help the body breathe.

It is worth noting that polio primarily infects children below five years old, according to WHO.

What causes polio?

This virus spreads from person to person mainly through the oral-fecal route, per the Centers for Disease Control and Prevention (CDC). It may contaminate food and water in unsanitary conditions. It infects people by entering the body through the mouth and spreading through contact with the feces of the infected person, or less commonly through droplets from a sneeze or cough of an infected person. The virus lives in the infected person's throat or intestines and may stay there for weeks.

A person infected with the poliovirus may spread the virus to others immediately before and up to 2 weeks after symptoms show up. Asymptomatic people may still pass the virus to others. An estimate by the CDC indicated 95% to 99% of people with polio are asymptomatic. This condition is called subclinical polio.

What are the symptoms of polio?

According to the CDC, most people infected with the poliovirus will not present visible symptoms. An estimate of about one in four people may have flu-like symptoms, such as:

  • Sore throat
  • Fever
  • Headache
  • Tiredness
  • Nausea
  • Stomach pain

The symptoms in non-paralytic polio, also known as abortive polio, usually resolve on their own in two to five days.

More serious symptoms of the poliovirus, present in a smaller portion of infected people, may affect the brain and the spinal cord in two ways:

  • Meningitis - An infection of the covering of the spinal cord and/or the brain; this occurs in about 1 to 5 cases for every 100 infected people.
  • Paralysis - About 1 in 200 people may not be able to move certain parts of the body or experience weakness in the arms, legs, or both. This is the most severe symptom of the virus since it may lead to permanent disability or even death. Paralytic polio may lead to paralysis in the spinal cord (also known as spinal polio), brainstem (bulbar polio), or both (bulbospinal polio).

Because poliomyelitis is classified as a paralytic disease, only people with the paralytic infection are considered to have polio. Paralytic polio may exhibit the same symptoms as non-paralytic polio before severe symptoms appear after a week. More serious symptoms may include:

  • Loss of reflexes
  • Loose and floppy limbs (sometimes on just one side of the body)
  • Severe spasms and muscle pain
  • Sudden paralysis (temporary or permanent)
  • Deformed limbs (especially hips, ankles, and feet)

It is rare for full paralysis to develop, according to WHO. However, around 2 to 10 out of 100 people with paralysis die due to the virus affecting the muscles involved in breathing.

Who is at risk for polio?

You are at risk if you have not been vaccinated against polio, or if you have been exposed to someone infected with the virus. If you have received an incomplete set of polio vaccines in your childhood, you may not be sufficiently protected from the disease.

You may also be at risk for polio if you are traveling to a country where there is a greater risk of getting the virus. Those working in a laboratory or healthcare setting and handling specimens such as feces containing the poliovirus are also at risk.

Furthermore, healthcare workers treating patients suspected of having polio may be at greater risk of contracting the virus. Similarly, if you are in close contact with a person who could be infected with poliovirus, you may be at risk.

Is there a polio vaccine?

Yes, there is a polio vaccine. It is often part of a series of routine childhood vaccines. The CDC has recommended children get vaccinated in four doses to stay protected against polio: one dose each at 2 months old, 4 months old, 6 to 18 months old, and 4 to 6 years old.

Inactivated polio vaccine or IPV is the only vaccine for polio given in the United States since 2000. It is a shot injected through the leg or arm. In other countries, the oral polio vaccine or OPV may be used. The CDC mentioned that IPV protects against severe disease in 99 out of 100 cases. Two doses of IPV provide 90% protection, and three doses provide at least 99%.

Also, according to the CDC, adults who have completed their polio vaccination but are at risk of contracting the poliovirus may receive one lifetime IPV booster. Some adults may not have received all four recommended doses of their polio vaccine, which may not fully protect them against polio. The CDC said completing the polio vaccination with IPV is a must.

Parents planning to travel internationally should make sure their children are fully vaccinated against the virus before their departure.

The polio vaccine is not recommended for persons with severe, life-threatening allergies. If you are moderately or severely ill, ask your doctor for advice on whether you should wait until full recovery before taking the vaccine.

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