Nigerian cases set back fight to eradicate polio

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In a serious setback to the drive to eradicate polio from the world, two cases of paralysis caused by the virus have been detected in northeast Nigeria, the World Health Organisation announced.

The New York Times reports that the discovery dashed the hopes of global health authorities to be able to declare the continent polio-free soon. Nigeria’s last case of wild polio virus was reported in July 2014. The continent’s last was reported in Somalia a month after that. The WHO requires three years with no confirmed cases before declaring a region polio-free.

“We are deeply saddened by the news,” Dr Matshidiso Moeti, the WHO regional director for Africa is quoted in the report as saying. “The overriding priority now is to immunise all children around the affected area.”

Until Thursday, the last known cases of paralysis caused by “wild” virus were all in Pakistan and Afghanistan. (Vaccination in many countries is still done with oral drops containing weakened live virus, which sometimes mutates to become more dangerous and start outbreaks of “vaccine-derived polio,” which also can paralyse. While alarming, those outbreaks can usually be brought under control quickly with further vaccination.)

The report says as recently as 2012, Nigeria accounted for more than half of all polio cases worldwide. Interrupting polio transmission in Africa was considered a major public health triumph. Only two diseases – smallpox and rinderpest, a veterinary disease – have ever been eradicated from the earth, and in both of them the last cases were found in Africa. The last few hundred cases of Guinea worm, or dracunculiasis, the only other disease as close to eradication as polio is, are also confined to Africa.

The report says genetic sequencing of the Nigerian virus suggests that the new cases were caused by a wild strain last detected in Borno State, Nigeria, in 2011, which implies that it circulated for five years without being detected. Raids by Boko Haram, the Islamic fundamentalist militia – including the kidnapping of 200 schoolgirls in Chibok two years ago – as well as fighting between Boko Haram and the Nigerian Army have made many areas off limits for vaccinators and surveillance specialists.

Massacres and fighting have driven thousands from their home villages. “That fluid movement of population complicates understanding of exactly where they’ve ended up,” said John F Vertefeuille, director of polio eradication for the US Centres for Disease Control and Prevention in Atlanta. “This is a setback, but we need to double our effort to make sure we interrupt transmission,” he added.

The report quotes Vertefeuille as saying that advances by the Nigerian Army this year have opened up new areas in Borno that were formerly off limits, and a case of paralysis caused by mutant polio vaccine was detected in March, prompting the increased surveillance that led to the discovery of the newest cases.

The Bill and Melinda Gates Foundation has taken over much of the cost of the polio eradication drive from Rotary International, which began it in 1988. The cost has recently been over $1bn a year. The report quotes the foundation as saying it was “deeply concerned” about the Nigeria cases but “remained strongly committed to supporting partners, governments and communities until the job is done.”

Full report in The New York Times

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