Ade Adepitan, the British Paralympic medallist and TV presenter whose Channel 4 documentary about polio in Nigeria airs on Monday night, says he is shocked it is still an issue after he contracted the disease there 37 years ago.
"It is the only country in Africa where it is still endemic," he said. "Somalia, Sudan have been able to make progress despite all their problems."
Nigeria is one of only three countries, alongside Afghanistan and Pakistan, that have failed to eradicate polio. Last year, 122 cases of the virus were reported, and there have been 40 confirmed cases this year.
Most polio cases in Nigeria are found in the predominantly Muslim north. In 2011, more than 95% of all cases occurred in Borno, Jigawa, Kano, Katsina, Kebbi, Sokoto, Yobe and Zamfara, the eight northern states where the disease is endemic.
Nigeria poses a significant risk to surrounding countries: in 2011, polio viruses originating from Nigeria were detected in five countries in west and central Africa. Despite dozens of vaccination campaigns over the years, only 65% of children in Borno, Kano, Sokoto and Yobe states have received four or more oral polio vaccine doses.
Vaccination campaigns have been dogged by rumours and conspiracy theories. In February, nine women who were vaccinating children against polio were shot dead in Kano, the biggest city in the north, apparently by Islamist militants, who claim the vaccines are part of a western plot to sterilise girls and wipe out the Muslim population.
For Adepitan and his team, who were scheduled to film in the area at the time, it was a close escape. "It was crazy and quite scary," he said. "The plan was to film coinciding with a vaccination campaign, but that was postponed after an assassination attempt on the emir of Kano, so we came back pretty upset, and suddenly heard this news. We would have been there, possibly interviewing. It was horrific."
Public sentiment against vaccination led to the suspension of campaigns in Kano in 2003, leading to a high number of children contracting the disease.
Suspicions about vaccination programmes go back even further. In 1996, Pfizer, the US pharmaceuticals firm, used an experimental drug during a meningitis outbreak in Kano; 11 children died and dozens became disabled as a result.
For Adepitan, lack of knowledge makes the local population receptive to the rumour-mongers. "When you look at the situation in the north, there are high numbers of people who are illiterate. That doesn't help," he said. "If somebody tells them something, they can't go on the internet to check whether it's just hearsay.
"There is also a mistrust of 'white medicine' … people who are in remote communities rarely have any contact with outsiders. All of a sudden, people come with vaccines, sometimes whites. They're going to be suspicious, thinking 'They've never come to help us before'."
Adepitan says the authorities have learned from their mistakes and now enlist authority figures such as tribal leaders and imams to support vaccination campaigns. "Unless you get them on board, it's not going to work," said Adepitan. "That's what [the authorities] are trying to do.