Washington, Jan 11 (IANS) The new Omicron subvariant XBB.1.5 is spreading quickly in the US, and is estimated to account for nearly 30 per cent of Covid-19 cases in the week ending January 7, according to the latest data from the Centers for Disease Control and Prevention (CDC). XBB.1.5 is projected to comprise more than 70 per cent of viruses in some northwestern regions in the country, Xinhua news agency reported citing the CDC data. XBB.1.5 made up 27.6 percent of the total cases in the week ending January 7, rising from 18.3 per cent from a week before and 11.5 per cent two weeks prior. The XBB variant has been driving up cases in parts of Asia, drawing concerns for its high infectiousness. Another two dominant Omicron subvariants BQ.1 and BQ.1.1 accounted for about 55 per cent of new Covid-19 cases in the US this week, the CDC said.