The SARS-CoV-2 virus acquires a new mutation in its genetic structure about every two weeks, according to the Centers for Disease Control and Prevention. Most mutations have no effect on how deadly or contagious the virus is.  But the variant known as B.1.1.7 could be more contagious—though not necessarily more deadly—than previous strains.

“It’s probably in more countries than we know,” Scarpino says of B.1.1.7, which was first identified in the United Kingdom. “That’s why we need the kind of widespread genomic surveillance the U.K. has instead of constantly playing catch-up.”