"It is with great hope that I declare that Covid-19 is no longer a health emergency of international concern," said WHO Director-General Tedros Adhanom Ghebreyesus, estimating that the pandemic had killed "at least 20 million" people, almost three times more than the official death toll of his organization.

He was pleased Thursday that weekly deaths from Covid-19 continued to fall, since peaking in China after restrictions were lifted there.

"This sustained trend has led to a return to "normal" in most countries and has strengthened the capacity of health systems to deal with potential resurgences and the burden associated with post-Covid-19 disease," known as Covid long, the WHO chief said.

"At the same time, there are still major uncertainties about the evolution of the virus, which makes it difficult to predict transmission dynamics or seasonality," he said.

For example, he noted that virus surveillance activities and genetic sequencing have significantly decreased worldwide, making it more difficult to track already known variants and detect new ones.