(Bloomberg) — The omicron variant of Covid-19, first identified in South Africa, has now been detected in countries from the U.S. to South Korea, underscoring the difficulties of curtailing contagious new strains. Most Read from BloombergReliving the New York Subway Map DebateChina Cash Flowed Through Congo Bank to Former President’s Cronies‘Pension Poachers’ Are Targeting America’s Elderly Veterans‘Ghost Signs’ Haunt London’s Reviving NeighborhoodsMost infections stem from travelers carrying t