LAST MONTH, Physics Harris was glued to the Covid-19 coverage that poured from his grandmother’s TV at all hours. Though thoroughly rattled, Mr. Harris saw opportunity, too. Within days, the 30-year-old, who runs his family’s screen-printing shop in Norcross, Ga., whipped up a coronavirus-themed T-shirt. Its graphic combines various virus motifs: Purell bottles, a coughing Tom Hanks, Rudy Gobert (the first NBA player to test positive) and young people wearing masks. To date, he has sold over 300 of the shirts at $20 a pop, mostly through Instagram.