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Africa declared free from wild polio — but vaccine-derived strains remain

No new cases of wild poliovirus have been recorded on the continent since 2016, but other types of the virus persist.

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NICEF health consultant Hadiza Waya tries to immunise a child during vaccination campaign against polio, Nigeria.

A health worker immunizes a child during a polio vaccination campaign in northwest Nigeria in 2017.Credit: Pius Utomi Ekpei/AFP/Getty

Africa is free from wild poliovirus, the World Health Organization (WHO) announced on 25 August — leaving just two countries where the virus remains endemic, Afghanistan and Pakistan.

The Africa Regional Certification Commission, an independent body responsible for overseeing the eradication of polio, has certified that all 47 countries in the WHO’s Africa Region have eradicated the virus after a long programme of vaccination and surveillance. There is no cure for the disease, which can cause irreversible paralysis and can be fatal if breathing muscles are affected, but vaccination can protect people for life.

The certification is a “historic” achievement, says Pascal Mkanda, coordinator of the polio-eradication programme at the WHO Regional Office for Africa in Brazzaville, Republic of Congo.

A region is certified as free of wild polio after three years have passed without the virus being detected in any of its countries. Africa’s last case of wild polio was recorded four years ago in northeast Nigeria. As recently as 2012, the country accounted for more than half of all polio cases worldwide. The challenges faced by those working to free Nigeria from wild polio included widespread misinformation about the vaccine, conflict and the difficulty of tracking nomadic populations that risked spreading the disease during their migrations, says Chima Ohuabunwo, an epidemiologist at Morehouse School of Medicine in Atlanta, Georgia. Ohuabunwo, who coordinated a project to support polio eradication in Nigeria, says that engaging with traditional and religious leaders was crucial in the effort to persuade parents to vaccinate their children.

Infographic: Polio today: Map showing worldwide polio cases recorded between August 2010 and 2020.

Source: WHO

Despite the eradication of wild poliovirus, Africa’s fight against polio isn’t over. In many countries, vaccination is done with oral drops containing a weakened form of the poliovirus, which sometimes mutates into a strain that can spread in under-immunized communities and cause paralysis. Since August 2019, more than 20 countries worldwide have reported cases of vaccine-derived polio (see ‘Polio today’). Because these outbreaks can usually be brought under control with further immunization, countries should continue to vaccinate as many people as possible, Ohuabunwo says.

Wild polio cases have decreased globally by more than 99% since 1988, but the virus is still endemic in Afghanistan and Pakistan, which report dozens of cases every year. To eradicate the disease, the two countries should focus on peace-building, reducing vaccine hesitancy, and boosting basic medical services and routine immunizations, says Zulfiqar Bhutta, a public-health researcher at Aga Khan University in Karachi, Pakistan.

Ohuabunwo hopes that the experience drawn from Africa will help to support eradication efforts in Pakistan and Afghanistan, because until wild polio is wiped out worldwide, all countries are at risk of a resurgence. “Polio anywhere is polio everywhere,” he says.

doi: 10.1038/d41586-020-02501-3

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