Pakistan has faced a fresh blow to its polio eradication efforts and accusations of a cover up, after officials confirmed an outbreak of a virus strain thought to have been stamped out.
Seven children have been paralysed in recent months after being infected by a type of virus that was considered eradicated, but formerly used in vaccination campaigns.
Officials were accused of trying to hush up the outbreak, which comes as the country's eradication efforts were already faltering, with a nearly seven-fold jump in cases since 2018.
A source told the Guardian that rather than announce the new outbreak, senior officials decided on a secret vaccination campaign to target the new strain.
But both the Pakistan government and the World Health Organisation denied a cover-up and said they had waited until the strain had been formally identified before announcing it. Britain's Department for International Development, which helps fund polio eradication in Pakistan, said it had known about the cases.
“Absolutely no cover-up,” said Zafar Mirza, the health minister. “Before we proceeded there was a need for a full genomic sequencing to determine the cause of the virus. The situation is under control.”
Global health workers have come close to eradicating the three different types of polioviruses with vaccines containing weakened versions of each strain. Type 2 of the wild virus was declared eradicated worldwide in 2015, and type 3 last month. Yet in rare cases the weakened virus used to create polio drops remains in sewage and mutates to become harmful again, infecting those who have not been vaccinated. These vaccine-derived outbreaks have been seen recently in Congo, Angola and Nigeria among other countries. After the wild strain of type 2 polio was eradicated, health officials began to remove it from vaccines.
A spokesman from the WHO said poliovirus type 2 was first detected in August.
"What is its source? That’s not clear at the moment. It is clear that it stems from a type 2-containing vaccine," he said.
He went on: “But it takes upwards of 8 weeks or more to fully confirm circulation of a poliovirus, due to lag times within the laboratory system. So this is what has now been fully received this week.”
Pakistan and Afghanistan are the only two countries where the wild polio virus remains. Pakistan had only 12 cases in 2018, but has already seen 80 so far in 2019.
The WHO said the wild type 1 poliovirus in Pakistan “is the comparatively more virulent strain and is more geographically widespread and therefore represents the greatest risk to the children of Pakistan.
“Therefore, the priority remains to continue to intensify efforts to eradicate WPV1 as urgently as possible, while continuing to protect children against other strains of poliovirus.”
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