http://www.newsweek.com/omicron-new-variants-ba-4-ba-5-what-know-cases-1697919 > Scientists are monitoring two newly characterized Omicron variant sub-types, BA.4 and BA.5, that have emerged in a few countries. > Throughout the year so far the Omicron BA.2 variant has spread to become generally the most common type after the BA.1-driven wave that saw record cases in the U.S. through the Christmas period.