In late August, the independent Africa Regional Certification Commission for Polio Eradication announced the elimination of wild poliovirus on the African continent. The last wild cases of the disease, which can cause debilitating paralysis and death, were found in the state of Borno in northeast Nigeria during the summer of 2016. Following a difficult few years in which the Global Polio Eradication Initiative suffered from a surge of cases in Pakistan and Afghanistan and the worldwide spread of cases associated with mutations of the polio vaccine, eliminating wild polio in Africa would be a stunning achievement and significant milestone. It now appears to be a done deal.
But an aerial view of Borno hints at why the story may not be so simple. Outside the walls of Maiduguri, the state’s capital city, lie a rugged and highly contested terrain that’s mostly inaccessible to health workers. Humanitarian hubs with camps for displaced citizens are largely accessible only by helicopter. In 2019, I worked with an international organisation, REACH, to obtain data on the needs of people from these inaccessible areas in support of humanitarian response efforts. What I saw there contradicts the conclusions of the World Health Organisation (WHO) and the Global Polio Eradication Initiative.
I believe that given the extreme inaccessibility caused by conflict, low vaccination rates, and logistical constraints that limit disease surveillance in many parts of rural Africa – a situation only made worse by COVID-19 – the declaration that wild poliovirus has been eliminated from the continent is premature.
The rush to declare victory reflects the chasm between high-level rhetoric and the day-to-day reality of life in Nigeria.
The eradication announcement comes after a four-year period in which the African continent has not recorded a case of wild polio. (A minimum of three consecutive years case-free is required to begin the certification process.) The Africa Regional Certification Commission granted its approval after reviewing documentation that Nigeria had met specific criteria indicating strong surveillance, such as detecting at least three non-polio cases of paralysis per 100,000 children under age 15 and testing the stool samples of at least 80% of paralysed children.
But eradication programs inherently operate on the fringes of detection capacity, and northeast Nigeria poses unique challenges. The Boko Haram insurgency, now more than a decade old, looms ever-present beyond towns like Maiduguri. Rural residents of contested areas face abduction, arbitrary killings, severe food insecurity, and routine arson of schools, health facilities, and shelters. Despite the surge of attention following the mass kidnapping in 2014 of schoolgirls in Chibok, child abductions remain commonplace.
The dangers are especially pronounced in Central Borno and the Sambisa Forest, where a faction of Boko Haram known as JAS has held large populations captive, destroyed health centres, and created a parallel health system that is unconnected to the polio surveillance network. Children in JAS territory are less likely to be vaccinated, and any polio cases in this part of Borno are more likely to go undetected.
A recent progress update published by the US Centres for Disease Control and Prevention cited the use of community informants, who encourage families of paralysed children to “temporarily leave insurgent-held areas” and travel to towns under government control, where they can be evaluated for polio. This makes little sense in practice. The harrowing journeys, which even under normal circumstances can take several days, would likely require an adult to carry a child overland at night. Families from the most dangerous areas, where insurgents often prevent civilians from traveling beyond their home villages, would be the least likely to take this risk simply for testing.
Polio vaccination teams have developed novel strategies for reaching some of these insurgent-held rural settlements. The teams sometimes travel with escorts from the Nigerian military; soldiers and members of local militias have sometimes also been trained to vaccinate children. These efforts have achieved partial success: Since January 2018, more than 140,000 children in these settlements, mostly in Northern Borno, have been vaccinated against polio.
Anecdotal reports, however, cast doubt on the effectiveness of these strategies. In 2019, an assessment conducted by REACH found that 73% of settlements in inaccessible areas reported the presence of unaccompanied children, whose parents had either previously fled or been killed or abducted. Participants in REACH’s focus group discussions reported that these children, told from an early age that the military will kill them on sight, flee into the brush at the sound of approaching vehicles, suggesting they may fly under the radar of vaccination teams.
REACH’s assessment of vaccination data from northeast Nigeria was dismal. In focus group discussions with individuals living in camps for displaced people, 79% of focus groups reported that their settlement’s most recent visit from a polio vaccination team predated several outbreaks detected from 2013 to 2016, and 16% reported that the most recent visit was more than a decade ago.
Settlements with reports of more recent vaccination visits were more likely to be located along main roads, pointing to the limited penetration of these vaccination campaigns. Undetected cases of polio could easily be infecting unvaccinated children who are unreachable.
In addition to case detection and vaccination, a third tool in the eradication arsenal is environmental surveillance. Samples of raw sewage collected from wastewater sites can help reveal circulating polio in regions where the virus may have infected one or more individuals without paralysing them. Environmental sampling requires concentrating large buckets of raw sewage and then searching the concentrate for poliovirus. Though there is a WHO-accredited polio lab in Maiduguri, transporting sewage samples from rural areas poses logistical difficulties, and so samples from outside the state capital are not tested routinely. Even within Maiduguri, the extreme heat in the region heightens the risk that any viruses will degrade before the samples can be tested. Detecting low-level transmission through environmental surveillance is likely impossible in the highest-risk areas of Borno in contested territory, which often lack sewage infrastructure in the first place, and where populations are too small and spread out to make environmental surveillance effective.
Other indicators fail to inspire confidence in the eradication declaration. A team of scientists who analysed a 2016 outbreak of wild polio cases saw genetic divergences that suggested the virus had been undergoing prolonged undetected transmission. And Nigeria has seen increasing cases of vaccine-derived polio, which emerge in rare instances when the weakened virus used in vaccines mutates into a more dangerous form that can infect unvaccinated children. Vaccine-derived polio spreads most easily in communities with low vaccination rates. So if these vaccine-derived cases were coming primarily from the hard-to-reach areas of Borno State – where vaccination is irregular at best – it would be a positive sign for the possibility of wild polio elimination. It would confirm that surveillance networks were capable of finding paralysed children in these areas. But of Nigeria’s 18 vaccine-derived polio cases reported in 2019, none were from insurgent-held regions where the challenges to vaccination and case detection are greatest.
Though countries are eligible for eradication certification after going three years without detecting a case, there is nothing magical about this timeline. It was derived from the smallpox eradication program, where three years represented three times the longest period between reported cases in a country – eight months – with an additional buffer year. The epidemiology of polio, which only causes paralysis in about one of every 200 cases, calls for a longer timeframe. And beyond epidemiological differences, a three-year certification period should not apply where populations have been held entirely captive for four or five years.
Despite these red flags, declarations of success have continued, ensuring that any future wild polio cases in Nigeria – or elsewhere in Africa – will be framed as a setback at best, or hidden at worst. A four-year absence of reported polio cases from Borno is insufficient evidence that wild poliovirus has been eliminated in Africa. Ignoring this reality may prove a shortsighted misstep for polio eradication: Any complacency in prevention efforts could allow the disease to come roaring back out of hiding. Senior leaders in the effort should not be so easily tempted by the lure of prematurely declaring victory.
Jordan Schermerhorn is a researcher working on infectious diseases in fragile states and conflict settings throughout sub-Saharan Africa.