The New York health department reported the country’s first case of polio in almost a decade on Thursday, which has sparked plenty of questions about whether polio was eradicated, who still gets vaccinated against the potentially paralyzing virus, as well as how it spreads.
In fact, Google queries for “is polio vaccine required in the U.S.” and “do kids get polio vaccines?” spiked more than 5,000% in the 24 hours after the news was reported, according to the Alphabet-owned
search engine’s trending search data. Questions about polio symptoms, how it spreads and whether the virus is airborne were also breakout Google searches following the new polio case.
So here’s what you need to know about polio, drawn from the World Health Organization and the Centers for Disease Control and Prevention.
What is polio?
Poliomyelitis (aka polio) is a very contagious, disabling and life-threatening disease caused by the poliovirus that largely affects children under 5. It spreads from person-to-person, and can infect the spinal cord, which can lead to paralysis. But it has been largely eradicated across the globe through vaccination.
What are some polio symptoms?
While 72 out of 100 people infected with the poliovirus won’t show any visible symptoms, one out of four people with poliovirus present the following flu-like symptoms that usually last two to five days:
A smaller proportion of people (less than one in 100) can develop more serious symptoms affecting their brain and spinal cord. These include paresthesia (feeling pins and needles in the legs) and meningitis (a spinal cord/brain infection.
But one in 200 infections can lead to irreversible paralysis or weakness in the arms, legs or both. And 5% to 10% of those paralyzed die when their breathing muscles also become immobilized.
The CDC notes that some kids who seem to recover from childhood bouts of polio can still develop muscle pain, weakness or paralysis as adults, somtimes 15 to 40 years later, in what is called post-polio syndrome.
Is polio contagious, and is polio airborne?
Polio is highly contagious, and spreads person-to-person most commonly through contact with the feces (poop) of an infected individual. Less commonly, it can spread from droplets sprayed by the sneeze or cough of an infected person.
The poliovirus, which only infects people, enters the body through the mouth and lives in an infected person’s throat and intestines. The virus can also live in an infected person’s feces for many weeks, and contaminate food and water in unsanitary conditions. The CDC explains that people can get infected by picking up small pieces of feces on your hands, and then touching your mouth. Or it can spread by putting objects (like toys) in your mouth if they have been contaminated with feces.
And yes, people with no symptoms can still spread the poliovirus and make other people sick. An infected person can spread the poliovirus immediately before symptoms appear, and up to two weeks afterward.
How is polio treated?
The WHO notes that there is no cure for polio, and what treatments that are available focus on alleviating or limiting symptoms, such as heat and physical therapy to stimulate muscles. Some antispasmodic drugs are used to relax the affected muscles, but there is no way to reverse permanent polio paralysis.
The best course of action against polio is to get vaccinated, health officials say. The two types of vaccines include an inactivated poliovirus vaccine (IPV) given as an injection in the leg or arm, depending on the patient’s age, which is the only inoculation against polio that has been given in the U.S. since 2000. And then there is the oral poliovirus vaccine (OPV), which is no longer licensed or given in the U.S. but is still used in some parts of the world. On rare occasions, the attenuated (live but weakened) virus in the oral polio vaccine can mutate and regain virulence. It appears the New York resident making headlines had a vaccine-derived strain of the virus, perhaps from someone who got a live vaccine. The Global Polio Eradication Initiative says that children are far more at risk from polio, however, than any side effects from the polio vaccine.
The CDC reports that 99 children to 100 out of 100 kids who get all four of the recommended doses of the inactivated polio vaccine will be protected from polio. And the WHO says that thanks to polio vaccines, more than 18 million people are able to walk today who would have otherwise been paralyzed by the poliovirus. But both health agencies warn that it takes just a single case to put the public at risk, with the most vulnerable people being those who never had a polio vaccine, those who never received all of the recommended doses, and those who travel to areas that could put them at risk of polio. This is why U.S. health officials are monitoring the New York case so closely.
Are polio vaccines still required in the U.S.? Do kids still get polio vaccines?
Yes, the CDC recommends that infants and children get four doses of the inactivated poliovirus vaccine, given by a shot in the leg or the arm, on the following schedule: one dose at 2 months old; one dose at 4 months old; one dose sometime 6 through 18 months old; and one more dose between 4 and 6 years old.
Health officials say most adults don’t need to get a polio vaccine if they followed the inoculation schedule as kids. There are three groups who are exceptions to this rule, however, who should consider getting vaccinated again, including:
Anyone traveling to a country where the risk of getting polio is greater.
Someone working in a laboratory and handling specimens that might contain polioviruses.
Healthcare workers treating patients who could have polio, or who have close contact with a person who could be infected with poliovirus.
The CDC says these adults should get three doses of IPV; one at any time, followed by a second dose one to two months later, and a third dose six months to a year after the second. Check with your healthcare provider. And adults who are at increased risk of exposure to poliovirus and who have previously completed a routine series of polio vaccines can also receive one lifetime booster dose of IPV.
Where is polio still found today?
The good news is that the Global Polio Eradication Initiative — which is spearheaded by national governments, WHO, Rotary International, the CDC, UNICEF, as well as the Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance — reports that wild poliovirus cases (as opposed to circulating vaccine-derived poliovirus, which is what may have caused the case in New York) have decreased by more 99% since 1988, plummeting from an estimated 350 000 cases in more than 125 endemic countries to 175 reported cases in 2019. There are three strains of wild poliovirus, and two of them have officially been certified as globally eradicated. But as of 2020, wild poliovirus type 1 still affects two countries: Pakistan and Afghanistan, particularly in the border areas.
The CDC says the United States has been polio-free since 1979 (meaning there is no year-round transmission of poliovirus in the United States) thanks to its vaccination program.
The Rockland County, N.Y. resident who tested positive appeared to have a vaccine-derived strain of the virus, perhaps from someone who got a live vaccine — available in other countries, but not the U.S. — and spread it. The CDC says it is consulting with the New York State Department of Health to investigate how and where the individual was infected, and to provide protective measures, such as vaccination services to the community to prevent the spread of polio to under- and unvaccinated individuals.