Any let up in the fight against polio risks a resurgence of the disease, leading to hundreds of thousands of cases of the deadly virus every year across the globe, one of the world's leading polio experts has warned.

Michel Zaffran, director of global polio eradication at the World Health Organization, told a press conference in advance of World Polio Day on October 24, that the world had never been so close to eradicating the disease, which used to kill and disable hundreds of thousands of children every year.

So far this year there have been just 22 cases of wild poliovirus in Afghanistan and Pakistan, down from a high of more than several hundred thousand cases a year in the 1980s.

“We are extremely close to eradicating wild poliovirus,” said Dr Zaffran. “When we started in 1985 there were over 125 countries where wild poliovirus was endemic and it was causing close to 300,000 cases of paralytic disease every year. We have reached a stage where we are closer than ever before to eradicating the disease.

He added that it was important to chase down the last few cases in order to wipe out the disease for good.