Global under-5 mortality decreased by 50% between 1990 and 2016. The UN Sustainable Development Goals (SDGs) call for under-5 mortality to be no greater than 25 deaths per 1000 livebirths. Since 1990, there has been tremendous progress towards this goal, with a reduction from 142 deaths per 1000 livebirths to 65 deaths per 1000 livebirths for the poorest quintile in low-income and middle-income countries (LMICs).1–2 Diarrhoeal diseases are estimated to result in 424 000 deaths in children younger than 5 years in 2017, making them the fourth leading cause of death after prematurity, birth trauma, and pneumonia.