Within a few more days, the team had electron microscope images of round viral particles, each particle encircled by a corona of knobs. This was so unexpected that one microscopist on the team had recourse to what amounted to a field guide; he browsed through a book of viral micrographs, looking for a match, as you or I might do for a new bird or a wildflower. He found his match among a group known as the coronaviruses, characterized by a corona of knobby proteins rimming each viral particle.
