Hundreds of millions of people may have already been infected with the novel coronavirus, far more than the current tally of around 35 million, according to the World Health Organization (WHO).
"Our current best estimates tell us that about 10% 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.
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 Covid-19 continues to surge in South-East Asia and is rising in Europe and the Middle East. In contrast, the situation on Africa and the Western Pacific region was more positive, he said.
Looking at the rising case numbers and at the upcoming influenza season on the northern half of the globe, WHO chief Tedros Adhanom Ghebreyesus urged countries to invest in the WHO-led programme on Covid-19 vaccines and medicines.
The programme to speed up research and to distribute products fairly to poorer countries is still 34 billion dollars short of its funding target, Tedros said.
"This is not charity," he said. "It’s the fastest way to end the pandemic and catalyze the global economic recovery."
The United States, which accuses China and the WHO of having covered up the emerging novel coronavirus disease, has not signed up to the initiative
Beijing has also not yet joined the dozens of countries that are funding the programme's vaccine projects.
"I will never tire of calling for solidarity," Tedros said.
"Finger-pointing will not prevent a single infection. Apportioning blame will not save a single life."