For COVID-19 researchers, the new year brings a strong sense of déjà vu. As in early 2020, the world is anxiously watching a virus spread in one country and trying to parse the risk for everyone else. This time it is not a completely new threat, but a rapidly spreading variant of SARS-CoV-2. In southeastern England, where the B.1.1.7 variant first caught scientists’ attention last month, it has quickly replaced other variants, and it may be the harbinger of a new, particularly perilous phase of the pandemic.

“One concern is that B.1.1.7 will now become the dominant global variant with its higher transmission and it will drive another very, very bad wave,” says Jeremy Farrar, an infectious disease expert who heads the Wellcome Trust. Whereas the pandemic’s trajectory in 2020 was fairly predictable, “I think we’re going into an unpredictable phase now,” as a result the virus’ evolution, Farrar says.