Mendy MucNulty, Andrew McNulty

Mendy McNulty swabs the nose of her son, Andrew, 7, Tuesday, July 28, 2020, in their home in Mount Juliet, Tenn. Six thousand U.S. parents and kids are swabbing their noses twice a week to answer some of the most vexing mysteries about the coronavirus. The answers could help determine the safety of in-class education during the pandemic. (AP Photo/Mark Humphrey)