Just as we thought that monkey smallpox would be a new viral scare for 2022, the UK Health Safety Agency (UKHSA) has declared a national incidence of recurrent polio virus detection in sewage in north and east London. Repeated positive readings for polio indicate that there is persistent infection and possible transmission in the area. This is something unexpected as the UK has 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 worldwide. It is caused by the polio virus, a small RNA virus that can damage cells in the nervous system.
It is not found in animals, so, like smallpox, it can be eliminated. And thanks to an effective vaccination campaign, we are getting closer to this goal every year.
There are three types of polio virus, and infection or immunization by one type does not protect against the other. The type 1 polio virus has continued to cause epidemics, but transmission by types 2 and 3 has been successfully disrupted by vaccination.
Poliovirus is spread through respiratory droplets, but it can also be transmitted from food or water that has come in contact with the feces of someone who has the virus.
It can survive at normal temperatures for several days. The last remaining outbreak has been linked to areas with poor sanitation that are difficult to achieve 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 virus from spreading to other countries.
The important role of vaccines
Vaccines are very important in eradicating polio. By 2021, there will be fewer than 700 reported cases worldwide.
In the UK, injectable polio vaccine is used. It contains inactivated virus (IPV) and is safe and effective in protecting immunized people from paralysis, but it is less effective at inducing local immunity in the gut, so vaccinated people can still become infected and shed the infectious virus, even though they may not show symptoms on their own. .
IPVs offer excellent protection for individuals, but are not sufficient to control outbreaks in poor sanitary conditions. The oral polio vaccine (OPV), which contains a live but weak virus, is suitable for this purpose. OPV is administered through drips and does not require trained staff or sterile equipment to administer, so that it can reach more communities.
This vaccine can induce strong intestinal immunity and it can prevent the shedding of wild polio virus. Because it contains a live virus, it can spread to close contacts of people who are immunized and protect them as well. It is also cheaper than IPV.
The disadvantage of using OPV is that a weakened virus can mutate, and in rare cases, it can revert to a variant that causes paralysis.
OPV is cleared by our immune system in a few days, but this may not happen in people with weakened immune systems who may carry the virus longer, increasing the chances of mutations. In less immunized countries, this can lead to a circulating vaccine -derived polio virus (VDPV). Naturally, the virus detected in London sewage was from a variety derived from a vaccine, type VDPV 2. There is still no wild polio virus in the UK.
Vaccine -derived polio can cause asymptomatic infection in people given the IPV vaccine, and it is spilled in the feces because there is no local intestinal protection with IPV. Therefore it can be detected in wastewater.
The detection method is sensitive, but a positive reading will not raise an alarm. VDPV Type 1 was recently detected in sewage in Kolkata. It is thought of from imported cases of vaccinated people with weakened immune systems who are unable to eliminate the vaccine strain from their bodies.
There are no reports of polio -related paralysis in the UK.
To prevent disease, we must ensure that family members keep abreast of the progress of their vaccines, especially children who may have skipped a course of vaccinations due to the COVID outbreak. IPV is safe, independent and effective in preventing polio. Unlike vaccines for smallpox which are in short supply and available to high -risk groups, IPV is available to everyone in the UK through their GP.
(Author: Zania Stamataki, Senior Lecturer in Viral Immunology, University of Birmingham)
(Disclosure Statement: Dr Zania Stamataki received funding from the Medical Research Foundation, Innovate UK and BCHRF and she shared her PhD students with AstraZeneca about iCASE MRC UKRI students.)
This article is republished from The Conversation under a Creative Commons license. Read the original article.
(Except for the headline, this story has not been edited by AGRASMARTCITY staff and is published from a syndicated feed.)