The World Health Organization (WHO) has warned that the new coronavirus variant Omicron is probably already present in most countries around the world.
Cases of the heavily mutated variant have been confirmed in 77 countries.
But WHO chief Tedros Adhanom Ghebreyesus said it was probably in many others that had yet to detect it, and was spreading at an unprecedented rate.
Dr Tedros said he was concerned that Omicron was being underestimated.
"Surely, we have learned by now that we underestimate this virus at our peril. Even if Omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems," he said.