The fast-spreading Omicron variant is now the dominant strain of Covid-19 in the United States.
Health authorities said that Omicron now accounts for 73.2 per cent of new US cases over the past week ending Saturday. The Centers for Disease Control and Prevention said that in some regions of the country it already comprises more than 90 per cent of new infections.
Early data suggests Omicron could be more infectious and possibly have higher resistance to vaccines. The early research though has suggested that it is not more severe than the Delta variant.
Also watch: Omicron cases doubling in 1.5 to 3 days, WHO says
Many countries have returned to harsh restrictions due to the Omicron explosion. But in the United States, President Joe Biden does not plan on "locking the country down," press secretary Jen Psaki said earlier in the day.
Since it was first reported in South Africa in November, Omicron has been identified in dozens of countries.
The WHO has called for nations to redouble efforts to help end the pandemic, calling for new year events to be cancelled because it was better to "celebrate later than to celebrate now and grieve later.