Mpox was declared a global health emergency on Wednesday for the second time in three years, as the World Health Organization urged action on a virus spreading rapidly through more than a dozen African countries.

The outbreak is most severe in the Democratic Republic of Congo, which has reported 15,600 mpox cases and 537 deaths, according to the U.N. agency. The mpox epidemic there has already proved more deadly than one in 2022, the last time an emergency was announced.