Cases of the omicron variant of the coronavirus popped up in countries on opposite sides of the world and many governments rushed to close their borders Cases of the omicron variant of the coronavirus popped up in countries on opposite sides of the world Sunday and many governments rushed to close their borders even as scientists cautioned that it’s not clear if the new variant is more alarming than other versions of the virus. The variant was identified days ago by researchers in South Africa, and much is still not known about it, including whether it is more contagious, more likely to cause serious illness or more able to evade the protection of vaccines. But many countries rushed to act, reflecting anxiety about anything that could prolong the pandemic that has killed more than 5 million people.