How many times have you seen the image? It looms behind newscasters during evening updates, gets handed out on printed fliers and scrolls by in tweet after tweet. It might even show up in your dreams.

But for Alissa Eckert — a medical illustrator at the Centers for Disease Control and Prevention who helped to create what has become the iconic representation of the novel coronavirus — it started out as just another assignment.

On Jan. 21, the day after the C.D.C. activated its emergency operations center for the new coronavirus, Ms. Eckert and her colleague Dan Higgins were asked to create “an identity” for the virus. “Something to grab the public’s attention,” she said. Ms. Eckert expected that whatever they came up with might appear on a few cable news programs, as their creations had in the past.

Instead, as the pandemic spread and intensified, their rendering’s reach did, too. “It started popping up around the world,” she said.