Late-night disco partying. Elbow-to-elbow seating in movie theaters. Mask-free baring of faces in public, especially in Europe and North America: Bit by bit, many countries that have been hard-hit by the coronavirus are opening up and easing their tough, and often unpopular, restrictive measures aimed to fight COVID-19 even as the omicron variant — deemed less severe — has caused cases to skyrocket.