The Omicron variant of the novel coronavirus is now the dominant source of new infections in the United States, accounting for roughly 73 percent of new infections nationwide, according to data from the Centers for Disease Control and Prevention (CDC). Federal officials on Monday cited CDC figures for the week ending Dec. 18 that showed a nearly six-fold increase in Omicron’s share of infections in only one week. The variant was first detected by doctors in Africa first less than a month ago, and on Nov. 26, the World Health Organization designated it as a “variant of concern.” The variant has since been reported in around 90 countries. CDC Director Dr. Rochelle Walensky said the new numbers reflect the kind of growth seen in other countries. “These numbers are stark, but they’re not surprising,” she said. Much about the Omicron variant remains unknown, including whether it causes more or less severe …