Ursula Mueller, Assistant Secretary-General for Humanitarian Affairs and Deputy Emergency Relief Coordinator in the UN Office for the Coordination of Humanitarian Affairs (OCHA), briefs reporters on World Humanitarian Day, at the UN headquarters in New York, on Aug. 19, 2019. The year of 2018 was the worst in five years for violence against aid workers, with at least 405 victims, Ursula Mueller said on Monday. (Xinhua/Li Muzi)