Yesterday, after a polio virus was discovered in a London sewer, UK public health officials declared doctors a “national incident” and urged doctors to watch out for polio cases and urged residents to check to see if they are currently ongoing. with his vaccination. time. rare disease. The source of the virus is still a mystery, but it is likely that someone outside the UK recently received an oral polio vaccine (OPV) that uses a live but attenuated virus and is no longer given in the UK.
Most polio infections are asymptomatic and no case has been detected in the UK. But with vaccination rates below 90%, there are concerns in some London communities that will not last. The outbreak of polio in London is a reminder that “no country is immune to re-infection with polio or recurrence until the disease is eradicated everywhere,” said Oliver Rosenbauer, a spokesman for the Global Initiative for the Eradication of Polio at the World Health Organization.
Polio has been eliminated from much of the world, but the virus is still endemic in Afghanistan and Pakistan, and 30 other countries in Africa, Europe and the Middle East are now labeled “outbreaks” of countries where the virus has recently circulated. The spread is triggered either by a wild virus that persists in Afghanistan or Pakistan, or by an OPV virus that has regained its ability to cause disease in unvaccinated people.
In the UK, the virus was detected in samples taken between February and June at Beckton Sewage Treatment Works, which cleans the sewage of 4 million people in north and east London. It did not trigger an alarm at first; Sewage monitoring programs in the UK typically detect a few such samples each year submitted by newcomers who have received OPV.
Such traces of sewage usually disappear fairly quickly. This time, the virus appeared in London for several months, and in recent samples, several closely related versions of the virus have emerged. Genetic changes indicate that the virus is evolving, a sign that it may spread to a small number of people.
Joseph Swan, the WHO’s Communications for Paralysis Officer, says the widespread spread is unlikely given the overall high vaccination coverage in the UK, which, like most wealthy countries, uses multiple doses of the destroyed virus vaccine. And he points out that there is still no direct evidence that the virus is spreading from person to person. However, officials encourage people to check that they and their children have received all the recommended doses of the vaccine.
The discovery of polio in London is the second this year in a place where the virus is not usually found. On March 7, an unvaccinated 3-year-old boy in Israel who was diagnosed with paralysis was diagnosed with polio, and the state detected poliovirus in 25 sewage samples this year, mostly in or near Jerusalem. The virus there is also a strain that originates from a vaccine, but it is a type 3 strain that is not related to the type 2 virus that was discovered in London. Rapid detection in both Israel and the United Kingdom shows that polio control systems are in place there, Rosenbauer says.
In response, Israel and the Palestinian Authority have stepped up vaccination efforts, and the virus has not been detected in sewage there since March. But COVID-19 has complicated the work, says Itamar Grotto, an infectious disease epidemiologist at Ben Gurion University in the Negev. Both staff and public health workers are exhausted by the pandemic and repeated vaccination campaigns against COVID-19, he says, and resistance to vaccination has increased in some groups.
Officials in London are now taking samples in sewer systems outside the Beckton treatment plant to see if they can narrow down the source of the virus and potentially more accurately target vaccination campaigns.
OPV, which has brought the virus to both the UK and Israel, has advantages in regions where the poliovirus is spreading. Not only is it cheap and easy to administer, but the live virus in the vaccine can still multiply in the recipient and trigger strong immune defenses in the gut that can stop further transmission of the virus and help boost the community’s defenses against future ones. . And although it is evolving from time to time to regain its virulence, health officials are beginning to introduce a more stable form of OPV, which they hope will reduce the risk of these recurrences.
Rosenbauer, meanwhile, says: “The most important thing states can do … is to ensure strict disease control and high vaccination coverage to reduce the risk and consequences of recurrence.”