Just as we thought monkeypox would be the new virus alert for 2022, the UK Health Security Agency (UKHSA) has declared a nationwide incident of repeated detection of poliovirus in sewage in north and east London. Repeated positive readings for polio suggest there is ongoing infection and likely transmission in the area. That’s unexpected since the UK has been declared polio-free since 2003. Here’s what you need to know.
Poliomyelitis (poliomyelitis) 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 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 with one type does not protect against another. Type 1 poliovirus continued to cause epidemics, but transmission by types 2 and 3 was successfully interrupted by vaccination.
Poliovirus is transmitted by respiratory droplets, but it can also be caught from food or water that has come into contact with the faeces of someone infected with the virus.
It can survive normal temperatures for several days. The last remaining outbreaks have been associated with areas with poor sanitation and hard to reach with vaccines. Afghanistan and Pakistan are the only two countries where wild polio is still endemic and are targeted for eradication programs to prevent the spread of the virus to other countries.
Crucial role of vaccines
Vaccines have played a crucial role in the elimination of poliomyelitis. In 2021, there were less than 700 reported cases worldwide.
In the UK, injected polio vaccine is used. It contains inactivated virus (IPV) and is safe and effective in protecting the immunized person against paralysis, but is less effective in inducing local immunity in the gut, so vaccinated people can still become infected and spread the virus. infectious virus, even if they cannot. show symptoms themselves.
IPV provides excellent protection for the individual, but is not sufficient to control an outbreak in poor sanitary conditions. The oral polio vaccine (OPV), which contains a live but weakened virus, is ideal for this purpose. OPV is administered by drop and does not require trained staff or sterile equipment to administer, so it can reach more communities.
This vaccine can induce strong intestinal immunity and it can prevent wild poliovirus shedding. Because it contains live virus, it can spread to close contacts of the immune person and protect them as well. It is also less expensive than VPI.
The downside of using OPV is that the weakened virus can mutate, and in rare cases, it can revert to paralysis-causing variants.
OPV is cleared by our immune system within days, but this may not be the case in people with weakened immune systems who can carry the virus for longer, increasing the risk of mutations. In underimmunized countries, this can result in the circulation of vaccine-derived poliovirus (VDPV). Indeed, the virus detected in London sewage belonged to the vaccine-derived variety, 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 it 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 trigger the alarm. Type 1 VDPV was recently detected in sewage from Kolkata. It is believed to be an imported case of a vaccinated person with a weakened immune system who was unable to clear the vaccine strain from their body.
No cases of polio-related paralysis have been reported in the UK.
To prevent illness, we need to make sure family members are up to date on their vaccinations, especially children who may have skipped a vaccination cycle due to the COVID pandemic. IPV is safe, free and effective in preventing poliomyelitis. Unlike monkeypox vaccines which are rare and available to high risk groups, IPV is readily available to everyone in the UK through their GP.
(Author: Zania Stamataki, 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 on an iCASE MRC UKRI Fellowship.)
This article is republished from The Conversation under a Creative Commons license. Read the original article.
(Except for the title, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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