Its appearance in sewer samples underscored fears the virus could spread back to countries once considered polio-free if it cannot be eradicated in its final pursuits.
The polio virus discovered in north and east London is believed to have been imported from abroad and originated from a weakened strain used in polio drops. In rare cases, this weakened virus used to mount an immune response mutates as it circulates in the population and reverts to a more harmful strain, infecting people who have not been vaccinated.
Polio teams in Pakistan have been attacked repeatedly for more than a decade. Two police guards were shot dead in several shootings in December and another was killed in January. In March, a female polio worker was shot dead.
Militancy, poverty and deep suspicion
Shehbaz Sharif, the Pakistani prime minister, said he was “deeply haunted” by the killings and ordered the interior minister to conduct an assessment.
A spokesman for UNICEF, the United Nations children’s body, said the dead were “among hundreds of thousands of heroes working selflessly to end polio”, adding: “We extend our condolences to families.”
Pakistan registered just one case of the polio virus in 2021, and until earlier this year there was a 15-month hiatus without any detection. However, the subsequent spike has again underlined how persistent the virus can be.
Pakistan and neighboring Afghanistan are the only two countries where the wild virus remains endemic. Both are conducting major internationally funded campaigns to eradicate the virus, while dealing with militancy, poverty and deep suspicion among some residents.