Researchers from Hokkaido University (Japan) and colleagues have identified 2-thiouridine (s2U) as a broad-spectrum antiviral ribonucleoside analogue, by phenotypic screening of a library of 753 nucleoside analogues for antiviral effects. s2U showed antiviral activity against several ssRNA+ viruses, including DENV, SARS-CoV-2 and its variants of concern.