The Delta Covid-19 variant, first identified in India, is quickly becoming the dominant strain of the coronavirus worldwide, the World Health Organisation said.
Soumya Swaminathan, the WHO’s chief scientist, said this was because of the Delta strain’s increased transmissibility.
The Delta strain tore through India and was partially responsible for a decision to pause lockdown-easing measures in England.
A top UK scientist warned on Saturday that a third wave of the virus is under way in the country after a 79 per cent rise in a week in Delta variant cases.
“It’s going up, perhaps we can be a little bit optimistic it’s not going up any faster, but nevertheless it’s going up, so this third wave is definitely under way,” said Adam Finn, a member of the Joint Committee on Vaccination and Immunisation, which advises the UK government.
“We can conclude that the race is firmly on between the vaccine programme, particularly getting older people’s second doses done, and the Delta variant third wave,” he told the BBC.
Russia's capital Moscow on Saturday reported a record number of cases for the second day running, with 9,120 new infections in the previous 24 hours.
Mayor Sergei Sobyanin said the Delta strain accounted for nearly 90 per cent of cases.
The US’s Centres of Disease Control and Prevention had already said on Friday that the Delta variant was rapidly spreading across the country.
"As worrisome as this Delta strain is with regard to its hyper-transmissibility, our vaccines work," Rochelle Walensky told Good Morning America. "I would encourage all Americans, get your first shot, and when you're due for your second, get your second shot and you'll be protected from this Delta variant."
It followed similar warnings from German health officials.
“It is really not a question of whether Delta becomes the leading variant, but only when,” said Lothar Wieler, the head of the Robert Koch public health institute. “It will have the upper hand in the autumn at the latest.”
Health minister Jens Spahn cautioned that the strain could “call into question the successes in fighting the pandemic”.