New ‘Variant of Concern’ Fuels Global Fear of Another Virus Surge

Scientists do not yet know how dangerous the new Omicron variant is, but its many mutations set off alarms, lowering hopes of putting the pandemic in the past.

The world reacted with alarm on Friday to the highly mutated new coronavirus variant discovered in southern Africa, as the United States, the European Union and nations across the globe imposed new travel restrictions, financial markets swooned and visions of finally emerging from the pandemic started to dim.

Just two days after the world learned of the variant, the World Health Organization officially labeled it a “variant of concern,” its most serious category — the first since the Delta variant, which emerged a year ago. The designation means that the variant has mutations that might make it more contagious or more virulent, or make vaccines and other preventive measures less effective — though none of those effects has yet been established.

After an emergency meeting, the W.H.O. warned in a statement that “preliminary evidence suggests an increased risk of reinfection with this variant” in people who have already had Covid-19. In keeping with the practice of naming variants for letters of the Greek alphabet, it dubbed the new one Omicron.