What you need to know about the disease

Written by Javed Iqbal

Polio can be eradicated and there are effective vaccines against it. (representative)

Birmingham, United Kingdom:

Just as we thought monkey pox would be the new virus scare for 2022, the UK Health Security Agency (UKHSA) declared a national incident of repeated detection of poliovirus in wastewater in north and east London. Repeated positive readings for polio suggest that there is an ongoing infection and likely transmission in the area. This is unexpected as the UK had been declared polio-free since 2003. Here’s what you need to know.

Poliomyelitis (polio) is a devastating disease that has historically caused paralysis and death around the world. It is caused by polioviruses, small RNA viruses that can damage cells in the nervous system.

It is not found in animals, so it can be eradicated like smallpox. And thanks effective vaccination campaignswe have come closer to this goal every year.

There is three types of poliovirus, and infection or immunization of one type does not protect against another. Type 1 poliovirus has continued to cause outbreaks, but transmission of types 2 and 3 has been successfully interrupted by vaccination.

Poliovirus is transmitted by respiratory droplets, but it can also be caught from food or water that has been in contact with the feces of a person who has the virus.

It can survive at normal temperatures for many days. The last remaining outbreaks have been linked to areas with poor sanitation, which are difficult to reach with vaccines. Afghanistan and Pakistan are the only two countries where wild polio is still endemic and targeted by eradication programs to stop the virus from spreading to other countries.

The crucial role of vaccines

Vaccines have been crucial in eliminating polio. In 2021 there was fewer than 700 reported cases around the world.

In the UK, the injected polio vaccine is used. It contains inactivated virus (IPV) and is safe and effective in protecting the immunized person from paralysis, but it is less effective in inducing local immunity in the gut, so vaccinated people can still become infected and excrete the infectious virus, even though they may not even showing symptoms.

IPV provides excellent protection for the individual, but is not enough to control an epidemic under poor sanitation. The oral polio vaccine (OPV), which contains live but attenuated virus, is ideal for this purpose. OPV is administered by drops and does not need trained personnel or sterile equipment to administer so that it can reach more communities.

This vaccine can induce strong intestinal immunity and it can prevent the secretion of wild poliovirus. Because it contains live viruses, it can spread to close contacts in the immunized person and also protect them. It is also cheaper than IPV.

The disadvantage of using OPV is that the attenuated virus can mutate and, in rare cases, it can return to paralytic variants.

OPV is removed by our immune system within a few days, but this may not be the case in people with weakened immune systems who can carry the virus longer, which increases the chance of mutations. In underimmunized countries, this can lead to circulating vaccine-derived poliovirus (VDPV). In fact, the virus detected in London’s wastewater was of the vaccine-derived variant, VDPV type 2. There is still no wild poliovirus in the UK.

Vaccine-derived polio can cause asymptomatic infection in IPV-vaccinated individuals and is excreted in the faeces because there is no local intestinal protection with IPV. It can therefore be detected in wastewater.

Detection methods are sensitive, but a single positive reading would not sound the alarm. Type 1 VDPV var recently discovered in wastewater in Kolkata. It is believed to be from an imported case from a vaccinated person with a weakened immune system who was unable to remove the vaccine strain from their body.

There is no reports of polio-related paralysis in the UK.

To prevent illness, we need to ensure that family members are up to date with their vaccinations, especially children who may have skipped a vaccination course due to the COVID pandemic. IPV is safe, free and effective in preventing polio. Unlike monkey pox vaccines, which are scarce and available to high-risk groups, IPV is readily available to anyone in the UK through their GP.The conversation

(Author: Zania StamatakiAssociate Professor of 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 student with AstraZeneca on an iCASE MRC UKRI student.)

This article was republished from The conversation under a Creative Commons license. Read original article.

(With the exception of the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

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