A dangerous mpox outbreak is unfolding in Sierra Leone. In just the first week of May, cases rose by 61%, and suspected cases surged by 71%. Roughly half of all confirmed mpox cases in Africa now come from this small West African nation. The virus is moving widely, across geographies, genders, and age groups.  And the virus is changing. Genomic analysis has revealed a fast-moving new variant of mpox—called G.1—that likely emerged in late November. At first it circulated silently but has since