Lagos-The World Health Organization (WHO) is set to certify on Tuesday that the African continent is free from wild polio, four years after the last cases appeared in northeastern Nigeria.

“Thanks to the relentless efforts by governments, donors, frontline health workers and communities, up to 1.8 million children have been saved from the crippling life-long paralysis,” the WHO said in a statement.

The official announcement is due at 1500 GMT in a video conference with WHO director-general Tedros Adhanom Ghebreyesus and key figures including philanthropist and Microsoft founder Bill Gates.

“Happiness is an understatement. We’ve been on this marathon for over 30 years,” said Tunji Funsho, a Nigerian doctor and local anti-polio coordinator for Rotary International. He said it marked a crucial step in the total eradication of the illness at the global level. “It’s a real achievement, I feel joy and relief at the same time,” he added. Poliomyelitis, or “wild polio” is an acutely infectious and contagious disease which attacks the spinal cord and causes irreversible paralysis in children. It was endemic around the world until a vaccine was found in the 1950s, though this remained out of reach for many poorer countries in Asia and Africa.

 As late as 1988, the WHO counted 350,000 cases globally, and in 1996 said there were more than 70,000 cases in Africa alone.