Hundreds of millions of people may have already been infected with the coronavirus, far more than the current tally of about 35 million, according to the World Health Organisation.
"Our current best estimates tell us that about 10 per cent of the global population may have been infected by this virus," WHO emergency operations chief Mike Ryan told the UN health agency's executive board on Monday in Geneva.
"It varies depending on country, it varies from urban to rural, it varies depending on groups. But what it does mean is that the vast majority of the world remains at risk," Ryan said.
"We are now heading into a difficult period. The disease continues to spread," he said.
There are currently 7.8 billion people in the world, according to UN statistics.
The share of people with COVID-19 varies among countries, between cities and urban areas and between social groups, Ryan said.
Even though the true number of cases is likely far higher than the reported numbers, the WHO estimate means that the vast majority of people have no antibodies and remain at risk of contracting COVID-19, the senior WHO official stressed.
Ryan said that outbreaks were surging in parts of southeast Asia and that cases and deaths were on the rise in parts of Europe and the eastern Mediterranean region.