Polio, a deadly disease that can paralyze children, is detected in London, New York and Jerusalem for the first time in decades, spurring renewed vaccination campaigns.
a terrible disease
Polio terrorized parents around the world in the first half of the 20th century. It mainly affects children under five and is often asymptomatic, but can also cause symptoms, including fever and vomiting. About one in 200 infections leads to irreversible paralysis, and of these patients, more than 10% die.
There is no cure for this disease, but since a vaccine was found in the 1950s, poliomyelitis has been completely preventable. Globally, the wild form of the disease has virtually disappeared. Afghanistan and Pakistan are now the only countries where the disease is highly contagious, spreading mainly through contact with feces, and remains endemic. But this year imported cases have already been found in Malawi and Mozambique – the first in these countries since the 1990s.
There are two main forms of poliovirus. Besides the wild form, there are still rare cases of what is called “vaccine-derived poliomyelitis”. It is this second form of the disease that has been detected in the sewage of the British capital, London, and in New York, in the USA, which reported a case in New York state. A genetically similar virus has been discovered in Jerusalem, Israel, and scientists are trying to understand the link, the Global Polio Eradication Initiative (GPEI) has said.
Globally, as of August 9, 19 cases of wild-type poliovirus and 223 of vaccine-derived poliovirus have been recorded this year, according to a report from the European Center for Disease Prevention and Control (ECDC), published this week. In 2022, the poliovirus has already been detected in 15 countries, with more than 90% attributed to the virus resulting from vaccines, also adds the European center.
Although vaccine-derived poliomyelitis is virtually unknown in the above locations, it is known that its a threat – though rare – in other countries, causing outbreaks every year, including 415 cases in Nigeria in 2021, for example.
This form of the virus results from the use of an oral polio vaccine which contains a live, weakened form of the virus. After being vaccinated, children excrete the virus in their stool for a few weeks. In communities with fewer vaccinated people, it can spread, mutate and even revert to a more aggressive version of the virus.
While countries like the UK and US no longer use this “live vaccine”, others still use it – mainly to stop outbreaks – which could allow the global spread of this form of the virus. , especially among people who started traveling again after the start of the covid-19 pandemic, experts have suggested.
After positive samples were detected in London sewage, UK authorities advised a booster dose of inactivated poliomyelitis vaccine for children aged one to nine in all London boroughs to ensure a high level of protection against the virus and to limit its spread.
Even so, experts agree that the biggest contributor to vaccine-induced outbreaks and wild-type outbreaks is still the undervaccinated population, says Derek Ehrhardt of the Centers for Disease Control and Prevention (CDC) the United States.
Vaccine hesitancy was a growing problem before the pandemic. Then Covid-19 caused even the worst disruption to routine vaccinations in a generation, according to the United Nations. In 2020, there were 1,081 cases of vaccine-derived polio, about three times more than the previous year. However, great efforts have been made to ensure that vaccination campaigns are back in force.
But the sewage test results are a wake-up call for parents and convey a key message, say scientists including David Heymann, an epidemiologist at the London School of Hygiene and Tropical Medicine: “Protect children through vaccination. “