VATICAN CITY (AP) — Pope Francis has denounced racism, likening it to a virus that lurks in waiting and continues to be shameful. Francis in a tweet on Sunday called racism “a virus that quickly mutates and, instead of disappearing, goes into hiding, and lurks in waiting.” Francis said “instances of racism continues to shame us.” He cited no particular instance. The United Nations marks March 21 as the International Day for the Elimination of Racial Discrimination. The pontiff said racism shows that “our supposed social progress is not as real or definitive as we think.”