Lessons from History: Historical WaSH Programmes and the Decline of Summer Diarrhoeal Mortality

Using high-frequency historical data on mortality (weekly) and temperature (daily), we examine the puzzle of the late decline of infant diarrhoeal mortality in British and Irish cities. While mortality from other faecal–oral diseases began falling before the 1880s alongside investments in urban water supply and waste disposal, large summer epidemics of infant diarrhoea persisted until the 1910s. We analyse a large panel of towns spanning the period 1893–1930 to characterise the temperature-infant mortality nexus and to identify turning points in this relationship. Two-way fixed effects models reveal the roles of flush toilet provision, reductions in fly populations, and infant feeding practices in the decline of infant diarrhoeal mortality. Our findings indicate that preventing lethal summer epidemics among young children required coordinated improvements in both domestic and environmental hygiene. We suggest that these findings provide historical support for contemporary calls for ‘transformative WaSH’ programmes.