A COVID-19 variant first identified in Southern California appears to have spread to at least 19 states and several other countries, a study published Thursday suggests. The variant accounted for about 44% of Southern California cases as of late January, nearly double from a month earlier, the study said. It was first identified in a single case in July and reemerged during a holiday surge in cases in the Los Angeles area. More research is needed to determine if the variant spreads more easily than other COVID-19 variants or causes more disease, said study co-author Jasmine Plummer, a Cedars-...