Health officials in the U.K. and U.S. are scrambling to forestall the return of polio after the virus that causes it was discovered spreading in New York and London, urging parents to ensure kids are vaccinated as rates dip after years of anti-vaxx conspiracies and widespread disruption during the Covid-19 pandemic.
Polio, also known as poliomyelitis or infantile paralysis, is a serious and life-threatening disease caused by the poliovirus that mainly, though not exclusively, affects children under five years of age.
Poliovirus enters the body through the mouth, is highly infectious and spreads easily from person to person, most commonly through contact with the feces of an infected person—often from poor handwashing—or, less frequently, through droplets when an infected person sneezes or coughs.
Most poliovirus infections are asymptomatic—around 70% of people experience no symptoms at all—and around one in four (25%) will experience mild symptoms like fever, headache, stomach pain, fatigue and nausea.
In a small proportion of cases, the virus invades the nervous system and causes more serious symptoms, most notably paralysis.
About one in 200 poliovirus infections lead to irreversible paralysis, according to the World Health Organization, and among those paralyzed patients, up to 10% die because the virus immobilizes muscles needed to breathe.
There is no cure for polio nor specific treatments targeting the virus—physical therapy can help improve long-term outcomes in some cases—but there are safe and effective vaccines that can provide lifelong protection.
Health officials in New York City on Friday announced that poliovirus had been detected in sewage, suggesting the virus has been circulating locally. The news came weeks after New York state reported the country’s first case of paralytic polio in about a decade. In recent months, poliovirus has also been found in wastewater samples in London and in children in Jerusalem. Data indicate the virus samples detected in Israel and the U.K. are genetically linked to the virus responsible for the New York case and suggest the virus may have been quietly spreading for some time over a wide geographic area.
What To Watch For
Vaccination campaigns. The discoveries sparked concern over a possible resurgence of polio in areas where local transmission has long been absent. After a number of children were found to be infected with poliovirus in Jerusalem, one of whom was paralyzed, Israeli officials launched a nationwide vaccination campaign to stave off a wider outbreak. London health officials have offered all children aged one to nine in the city a dose to strengthen protection against the virus. Experts say the overall risk of polio is low as there is a high degree of protection from vaccination among the general population. No mass vaccination campaign has been announced in New York State or New York City but officials and health experts have urged parents to ensure children are vaccinated against the disease and for unvaccinated or incompletely vaccinated adults to get immunized.
Before the rollout of vaccines, polio was one of the most feared diseases. It killed and disabled tens of thousands of people, mostly children, every year and outbreaks would often shutter swimming pools and nurseries and prompt parents to keep children inside. The development of the first polio vaccine was the product of a huge national effort and parents volunteered some 2 million children to take part in the trials. Vaccination can confer lifelong protection and has eliminated poliovirus from most of the world. It is required for entry into kindergarten in every state and Washington, D.C., usually for both public and private schools and sometimes for homeschools as well. Some states offer exceptions on medical, philosophical or religious grounds. Experts warn that coverage has slipped to dangerously low levels amid the spread of anti-vaxx conspiracy theories and disruptions to routine immunization during the Covid-19 pandemic. Two kinds of vaccines are deployed, one using an inactivated virus that must be injected and another using a live virus that has been weakened so it cannot cause paralysis (this is given orally). The weakened virus can spread in under-immunized communities—this can provide immunity to others who didn’t receive the vaccine—but it sometimes mutates into a strain that can cause paralysis. Rarely, this can circulate in a community like the wild virus. Vaccination still protects against vaccine-derived poliovirus and over the last 10 years there have been fewer than 800 cases globally (more than 6.5 million children would have been paralyzed without oral vaccination during that time). Vaccine-derived virus is what has been found in New York, London and Jerusalem. British and American officials say the virus must have been imported from someone vaccinated with the live vaccine as both nations use the inactive shot for their programs.
What To Watch For
Eradication. As poliovirus has only ever been found in humans the virus is considered particularly susceptible to eradication. Thanks to a concerted global campaign, the number of wild poliovirus cases—caused by naturally occurring, rather than vaccine-derived, viruses—have decreased by over 99% since 1988, from an estimated 350,000 cases in more than 125 endemic countries then, to just 6 reported cases in 2021. Endemic transmission of wild poliovirus continues in just two countries: Afghanistan and Pakistan. Africa was declared free of wild poliovirus in 2020 and no wild poliovirus has been detected on the continent since 2016. Vaccine-derived strains of the virus persist, however.
20 million. That’s how many people are able to walk today who would have otherwise been paralyzed by polio thanks to vaccination efforts since 1988, according to the WHO. In that time, some 3 billion children have been immunized against polio and an estimated 1.5 million childhood deaths prevented through the giving of vitamin A during polio vaccination activities, the organization said.
Polio: An American Story (Book by David Oshinsky)
Map: These states lag in polio vaccinations (NBC News)