On Feb. 28, 2020, immediately after Christian Drosten published a genetic sequence of the novel coronavirus online, he took to Twitter to issue a warning. As the virus has raced around the world, more than 350 genome sequences have been shared on the online platform GISAID.

They held clues to how the new virus, named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was spreading and evolving.