Polio can be eradicated and there are effective vaccines against it. (representative)
Birmingham, United Kingdom:
Just as we thought monkeypox would be the new viral fear for 2022, the UK Health Security Agency (UKHSA) has announced a national incident with the re-discovery of poliovirus in the sewers in north and east London. Recurrent positive indications for polio suggest that there is ongoing infection and probable transmission in the area. This is unexpected, as the United Kingdom has been declared polio-free since 2003. Here’s what you need to know.
Polio (polio) is a devastating disease that has historically caused paralysis and death worldwide. It is caused by polioviruses, small RNA viruses that can damage cells in the nervous system.
It is not found in animals, so, like smallpox, it can be destroyed. And thanks to effective vaccination campaigns, we are approaching this goal every year.
There are three types of polioviruses, and infection or immunization of one type does not protect against another. Type 1 poliovirus continues to cause epidemics, but type 2 and 3 transmission has been successfully stopped by vaccination.
The poliovirus is transmitted through respiratory droplets, but can also be caught by food or water that has been in contact with the feces of someone who has the virus.
It can survive at normal temperatures for many days. The last remaining outbreaks are related to areas with poor sanitation, which are difficult to access with vaccines. Afghanistan and Pakistan are the only two countries where wild polio is still endemic and are targeting eradication programs to stop the virus from spreading to other countries.
Crucial role of vaccines
Vaccines have been crucial in eliminating polio. In 2021, there are less than 700 reported cases worldwide.
An injectable polio vaccine is used in the United Kingdom. It contains inactivated virus (IPV) and is safe and effective in protecting the immunized person from paralysis, but is less effective in inducing local immunity in the gut, so that vaccinated people can still become infected and shed the infectious virus, although they may not show symptoms on their own.
IPV offers excellent protection for the individual, but it is not enough to control an epidemic in poor sanitation. The oral polio vaccine (OPV), which contains a live but attenuated virus, is ideal for this purpose. OPV is applied in drops and does not require trained staff or sterile administration equipment, so it can reach more communities.
This vaccine can cause strong intestinal immunity and can prevent the release of wild polioviruses. Because it contains a live virus, it can spread to close contacts of the immunized person and protect them. It is also cheaper than IPV.
The disadvantage of using OPV is that the attenuated virus can mutate and in rare cases can return to variants that cause paralysis.
OPV is cleared from our immune system within days, but this may not be the case in people with a weakened immune system, who can carry the virus longer, increasing the likelihood of mutations. In poorly immunized countries, this can lead to circulating poliovirus produced by vaccines (VDPV). In fact, the virus found in a London sewer was a vaccine-derived type, VDPV type 2. There is still no wild poliovirus in the UK.
Vaccine-derived poliomyelitis can cause asymptomatic infection in people vaccinated with IPV and is excreted in the faeces because there is no local protection of the gut with IPV. It can therefore be found in wastewater.
Detection methods are sensitive, but a positive reading would not be alarming. Type 1 VDPV was recently discovered in the sewers in Kolkata. It is thought to have been imported from a vaccinated person with a weakened immune system who was unable to eliminate the vaccine strain from his body.
There have been no reports of polio-related paralysis in the United Kingdom.
To prevent the disease, we must ensure that family members keep up with their vaccinations, especially children who may have missed a vaccination course due to the COVID pandemic. IPV is safe, free and effective in preventing polio. Unlike monkeypox vaccines, which are in short supply and available to high-risk groups, IPV is readily available to anyone in the UK through a GP.
(Author: Zania Stamataki, Senior Lecturer in Viral Immunology, University of Birmingham)
(Disclosure Statement: Dr. Zania Stamataki receives funding from the Medical Research Foundation, Innovate UK and BCHRF and she shares a PhD with AstraZeneca’s iCASE MRC UKRI student.)
This article is republished by The Conversation under a Creative Commons license. Read the original article.
(Except for the title, this story was not edited by NDTV employees and was published by a syndicated channel.)
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