Yesterday, after declaring a poliovirus in London’s sewage, declaring it a “national event”, UK public health officials asked doctors to be vigilant in the face of polio cases and asked residents to check if the vaccines were up to date. a rare disease. The source of the virus is still a mystery, but it was probably someone outside the UK who recently used the oral polio-polio vaccine (OPV), a live but weakened virus that is no longer available in the UK. .
Most polio infections are asymptomatic, and so far no case has been found in the UK. But with some London communities having vaccination rates below 90%, there is concern that it will not last. The appearance of the poliovirus in London reminds us that “no country is re-infected or re-infected with polio until the disease has been eradicated everywhere,” says Oliver Rosenbauer, a spokesman for the World Health Organization’s global polio initiative. .
Polio has become extinct in 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 designated “outbreak countries” where the virus has recently circulated. The spread is due to the growing virus in Afghanistan or Pakistan or the OPV virus that has regained its ability to cause disease in people without vaccines.
In the UK, the virus was detected in samples taken from February to June at the Beckton Sewage Treatment Works, which processes wastewater from 4 million people in north and east London. At first he did not sound the alarm; The UK’s wastewater control programs often detect such samples every year by throwing in new arrivals who have received OPV.
Traces of such dirty water usually disappear quite quickly again. This time, the virus continued to appear in London for several months, and several versions with a close link to the virus appeared in recent samples. Genetic changes suggest that the virus continues to evolve, a sign that it is spreading in a few people.
Joseph Swan, WHO’s head of polio communication, says the wider spread is difficult because of the high overall vaccine coverage in the UK, as most rich countries use multiple doses of a dead virus vaccine. And he points out that there is still no direct evidence that the virus is spreading from one person to another. But officials are encouraging people to check that they and their children have received all the recommended doses of vaccine.
Detection of poliomyelitis in London is the second this year in a place where the virus is not common. On March 7, a 3-year-old child without Israeli vaccine who developed paralysis was diagnosed with polio, and the country has detected a poliovirus this year in samples of 25 sewage, mostly in or around Jerusalem. The virus in it is also a strain derived from the vaccine, but it is a type 3 strain that has nothing to do with the type 2 virus detected in London. Rapid detection in Israel and the United Kingdom proves that its polio surveillance systems are working, Rosenbauer says.
Israel and the Palestinian National Authority have stepped up their efforts to respond to the vaccine, and no virus has been detected in the sewage since March. But COVID-19 has made the job harder, says Itamar Grotto, an infectious disease epidemiologist at Ben-Gurion University in the Negev. Both public and public health workers say they are tired after numerous pandemic and COVID-19 vaccination campaigns, and in some groups vaccination doubts have increased.
Officials in London are taking samples from sewer systems above the Beckton treatment plant to see if they reduce the source of the virus and perhaps target vaccination campaigns more specifically.
The OPV, which 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, it can also replicate the live virus in the vaccine to the recipient, providing strong immune protection in the intestines that can stop further transmission of the virus, helping to increase community defenses against future outbreaks. And although it occasionally evolves to regain its virulence, health care providers have begun to deploy a more stable form of OPV as they hope to reduce the risk of these delays.
Meanwhile, Rosenbauer says, “The main thing countries can do … is ensure strong disease surveillance and high vaccine coverage to minimize the risk of recurrence and the consequences.”