CDC Director Rochelle Walensky

The lawsuit, filed in federal district court in Tampa, asks a federal judge to lift restrictions imposed by the CDC that have idled cruise ships in the U.S. for more than a year because of the pandemic.

"The pandemic illuminated inequities that have existed for generations and revealed for all of America a known, but often unaddressed, epidemic impacting public health: racism," Walensky said.

The variant known as B.1.1.7, which is more easily spread, was first identified in England last fall. Since then, it has spread quickly in the U.S.

President Joe Biden urged governors to reinstate mask mandates and other restrictions that some states have been easing.

With new cases teetering at about 60,000 to 70,000 per day, new hyper-transmissible variants and state rollbacks of coronavirus restrictions, the CDC chief urges Americans to remain vigilant.