Federal health officials warned on Friday that a far more contagious variant of the coronavirus first identified in Britain could become the dominant source of infection in the United States by March, and would likely lead to a wrenching surge in cases and deaths that would further burden overwhelmed hospitals.

This dire forecast from the Centers for Disease Control and Prevention made plain what has been suspected for weeks now: The nation is in an urgent race to vaccinate as many Americans as possible before the variant spreads across the country…

Privately, one C.D.C. official said the prospect of the new variant’s prowess was “chilling,” and underscored the urgent need for people to follow precautions. A bulletin released by the agency — which used highway emergency sign imagery to warn of rising cases, strained hospitals and new more contagious variants — conveyed the sense of urgency. “More spread, more cases, more deaths,” it warned.