The problem is even bigger than expected. The actually eradicated polio virus, which can cause paralysis, was not only found in London’s sewage. The sewage treatment plants of five counties in the US state of New York, including the Big Apple itself, have already detected it. In view of this widespread spread of the virus, Governor Kathy Hochul declared a state of emergency on September 9 – and called on the unvaccinated to get immunized against polio.
The findings mean that the pathogen that causes polio is actively infecting new people, who then excrete the virus, which in turn can be detected in the wastewater. According to the World Health Organization (WHO), the disease is mild in 90 percent of cases. Patients, including adults, only have stomach problems. However, if the virus spreads to the nervous system, irreversible muscle paralysis and even fatal paralysis of the respiratory muscles can occur.
First paralysis also of older people
In Rockland County, New York State, a 24-year-old man was seriously ill with polio in July and, according to media reports, was paralyzed by the infection. It was the first case of polio in the States in more than a decade. Israel also reported polio virus finds in several sewage treatment plants and some sick children in March.
The new cases surprised many. By contrast, it was only a matter of time for public health researchers intent on eradicating the virus for good. In a tightly networked world, the disease, which was believed to be largely contained, has apparently made its way back via one of the vaccines of all things. Despite vaccination efforts, the wild virus is only circulating in Afghanistan and Pakistan.
The theory: The weakened polio pathogens of the original oral vaccination regained their ability to reproduce through mutations and then infected unvaccinated people. This oral vaccination is no longer used in Europe and the USA – also because of this danger. However, it is still used in African and Asian countries because it is so easy to give. To the disadvantage of the mutation risk comes a major advantage: the vaccination ensures almost complete sterile immunity in the intestinal mucosa. This means that the viruses do not cause an infection, i.e. no transmission of new viruses, even if polio should be resumed via a smear infection.
Syringe with disadvantages
With the newer, injectable polio vaccine, on the other hand, there is no risk of mutation because it uses inactivated viruses. However, this systemic immunization has a lower overall effect. Although you do not become ill symptomatically, you may still become infected, produce new viruses and pass them on. The intramuscular vaccination only protects the vaccinated, but not the people around them – we know this effect well enough from the Sars-CoV-2 coronavirus.
The US health authorities are now increasingly relying on sewage monitoring, which they only started after the London finds. Unlike London, the polio outbreak appears to be more widespread in upstate New York. The US authorities therefore hope that as many people as possible will follow their call and get vaccinated against polio or have their vaccination refreshed. That would at least prevent serious consequences of infection and slow down the transmission of the virus somewhat.
Meanwhile, a new oral vaccination that is being tested for safety in a phase 3 study in Gambia in children between the ages of one and five is giving hope for a stronger stop in transmission. It also relies on a weakened virus. However, researchers have locked this in a kind of genetic cage, says Raul Andino-Pavlovsky from the University of California in San Francisco, who helped develop the vaccine. New genetic changes should prevent the pathogen from being able to reproduce again.
Safe oral vaccination
The investigation is not yet complete and further efficacy studies may be necessary. On the basis of a WHO emergency approval, more than 100 million people have already received the vaccine. According to Andino-Pavlovsky, no virus variants capable of replication have been discovered so far. In total, 22 countries received more than 450 million vaccine doses.
Deployment prior to the completion of important studies raises questions and experts are divided on whether this is the right path to take. Rare side effects can only be detected in larger studies, criticized Abdhalah Ziraba, epidemiologist at the African Population Research Center in Nairobi in the journal “Nature”. There is also a lack of urgency for emergency approval.
However, other experts such as Nicholas Grassly from Imperial College in London argue that only with the new vaccine can the constant new seeding of infectious polio viruses be interrupted – and thus further mutants.
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