New CDC reports warn that variants could lead to "rapid rise" in Covid-19 cases From CNN's Jamie Gumbrecht Two new reports from the US Centers for Disease Control and Prevention warn that new coronavirus variants could lead to a rapid rise in the numbers of Covid-19 cases. In one report released Wednesday, researchers from the CDC and Minnesota health department detailed cases of the B.1.1.7 variant, first identified in the United Kingdom. Earlier modeling data suggested this variant, which may be more transmissible, could become the predominant variant in the United States in March, and the CDC has urged people to take action to reduce spread.