On Wednesday 22 June, the UK health security agency (Ukhsa), a British health security agency, released a note joint with the national drug agency (Mhra) in which it confirms that it has found traces of polioviruspathogen responsible for the polio, in wastewater samples collected from the treatment plant serving the north-east quadrant of London in the United Kingdom. It would be a virus, traces of which were also found between February and last May, deriving from the live attenuated one present in oral vaccines and that, in very rare cases, it can lead to paralysis in unvaccinated people.
Notwithstanding that no cases of infection with poliovirus nor of paralysis, investigations are underway to shed light on the issue and understand the origin and spread of the pathogen. Meanwhile, citizens are advised to check their polio vaccination status, especially parents of unvaccinated young children.
Polio, symptoms and methods of contagion
The polio (or simply polio) is one severe infectious disease affecting the central nervous system and that it is caused by three different types of poliovirus, pathogens belonging to the genus of enteroviruses they are transmitted by the fecal-oral route, that is through the ingestion of water or contaminated food, or with direct contact between people, through saliva and droplets emitted during breathing. Once it has entered the body, the poliovirus multiplies in the cells of the oral mucosa, in the intestine and in the lymphatic tissues associated with them, also spreading through the I did before the typical symptoms of the disease appear. From the intestine, then, within a few hours, the virus invades the nervous systemdestroying neurons and, in a minimal part of infections (about 1%), causing paralysis irreversible which in the most serious cases can be seriously disabling and even, involving the muscles involved in breathing, fatal.
Throughout history, polio has spread among humans with several epidemic wavesreaching notable peaks in Western countries during the 1950s and 1960s: for example, like reports the Higher Institute of Health (Iss) in Italy, in 1958, over 8 thousand cases were notified. Although there are no specific therapies for this disease, to date polio has been declared eradicated in most of the countries of the world thanks to the intense vaccination campaigns which began in the last century. The vaccinesin fact, by preventing poliovirus infection, they are the only way to avoid the serious complications associated with polio. There are two different types of vaccines: that a virus inactivatedto be administered by intramuscular injection, and that a live attenuated virusin which the poliovirus is indeed alive but treated in such a way that it loses the characteristics responsible for its virulence, to be administered orally. Due to its ease of administration and the ability to confer long-term immunity, it was precisely the oral vaccine a virus attenuated a allow the eradication of polio in Europe and other countries and is still recommended by the World Health Organization (WHO) in its global disease eradication campaign.
The assumptions of the health authorities
However, precisely because the most widely used vaccine is the oral one, in which the attenuated poliovirus passes through the gastrointestinal tract of vaccinated people, it is normal for them to be detected every yearsporadically and in cases completely isolated from each other, 1 to 3 polioviruses associated with the oral vaccine. What worries the health authorities this time, the document reads, is the fact that the detected virus appears to be closely related to others identified in the same waste water Londoners between February and May 2022. Based on the information available, health authorities have hypothesized that a person vaccinated abroad with the live oral polio vaccine (in an area possibly with low vaccination coverage and where the poliovirus is widespread) traveled to the UK , spreading the virus resulting from the vaccine by direct contact and through the faeces. The poliovirus then continued to evolveuntil it becomes a so-called vaccine-derived poliovirus.