What you need to know about the disease

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

Birmingham, UK:

Just as we thought monkeypox would be the new virus scare for 2022, the UK Health Safety Agency (UKHSA) has declared a nationwide incident of repeated poliovirus detection in sewage in the north and north. East London. Repeated positive readings for polio suggest there is an ongoing infection and probable transmission to the area. This is unexpected since the UK 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 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, therefore, like smallpox, it can be eradicated. And thanks to effective vaccination campaigns, we are getting closer to this goal every year.

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

Poliovirus is transmitted by respiratory droplets, but it 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 in normal temperatures for many days. The last remaining outbreaks have been associated with areas with poor sanitation that are difficult to reach with vaccines. Afghanistan and Pakistan are the only two countries where wild polio is still endemic and are targeted by eradication programs to stop the spread of the virus to other countries.

Crucial role of vaccines

Vaccines have been instrumental in eliminating polio. In 2021, fewer than 700 cases were reported worldwide.

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 is less effective in inducing local immunity in the gut, so vaccinated people can still become infected and spread infectious viruses, even though they may not show the symptoms themselves.

IPV offers excellent protection for the individual, but it is not sufficient to control an epidemic in poor sanitation. The oral polio vaccine (OPV), which contains live but weakened viruses, is ideal for this purpose. OPV is administered by drops and does not require trained personnel or sterile equipment for administration, so it can reach more communities.

This vaccine can induce powerful intestinal immunity and can prevent the spread of wild polioviruses. Since it contains live viruses, it can spread to close contacts of the immunized person and also protect them. It is also cheaper than IPV.

The disadvantage of using OPV is that the weakened virus can mutate and, in rare cases, can revert to variants that cause paralysis.

OPV is cleared from our immune system within days, but this may not be the case for people with weakened immune systems who can carry the virus for longer, increasing the chance of mutations. In countries under immunized, this can lead to the circulation of vaccine-derived poliovirus (VDPV). In fact, the virus detected in London’s sewage was of the vaccine-derived variety, VDPV type 2. Wild poliovirus does not yet exist 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 intestinal protection with IPV. It can therefore be detected in wastewater.

The detection methods are sensitive, but a single positive reading would not raise the alarm. Type 1 VDPV was recently detected in wastewater in Calcutta. It is thought to come from an imported case from a vaccinated person with a weakened immune system who was unable to eliminate the vaccine strain from their body.

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

To prevent disease, we need to ensure family members are up to date with their vaccinations, especially children who may have missed a vaccination course due to the COVID pandemic. IPV is safe, free and effective for preventing polio. Unlike monkeypox vaccines which are in short supply and are available to high-risk groups, IPV is readily available to everyone in the UK through their GP.The conversation

(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 shares a PhD student with AstraZeneca on an iCASE MRC UKRI Scholarship.)

This article was republished by The Conversation under a Creative Commons license. Read the original article.

(Except for the title, this story was not edited by the NDTV staff and is posted by a syndicated feed.)

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