Omicron has raced ahead of other variants and is now the dominant strain of the coronavirus in the United States, accounting for 73 percent of new infections last week.
The US Centers for Disease Control and Prevention (CDC) numbers on Monday showed nearly a six-fold increase in Omicron’s share of infections in only one week.
The national rate suggests that more than 650,000 Omicron infections occurred in the US last week.
“These numbers are stark, but they’re not surprising,” CDC Director Dr Rochelle Walensky said to reporters.
WHO designated Omicron a variant of concern on 26 November, soon after it was first detected by scientists in South Africa, and much is still not known about it.
Scientists remain uncertain how dangerous it is, but early data suggests it can be more resistant to vaccines and more transmissible than the Delta strain.
In an update, WHO said Omicron has been reported in 91 countries.
