Background: Description of diarrhoeal clusters in time and space and understanding seasonal patterns can improve surveillance and management. The present study investigated the spatial and seasonal distribution, and purely spatial, purely temporal, and space-time clusters of childhood diarrhoea in Southern Ethiopia.

Methods: We analyzed data from the Health Management Information System (HMIS) under-five diarrhoeal morbidity reports from July 2011 to June 2017 in 19 districts of Sidama Zone, southern Ethiopia. The Kulldorff’s SaTScan software with a discrete Poisson model was used to identify statistically significant special, temporal, and space-time diarrhoea clusters.

Results: A total of 202,406 under-five diarrhoeal cases with an annual case of 5,822 per 100,000 under-five population were reported.  An increasing trend of diarrhoea incidence was observed over the six years with seasonal variation picking between February and May. The highest incidence rate (135.8/1000) was observed in the year 2016/17 in Boricha district. One statistically significant most likely spatial cluster and six secondary clusters were identified. One statistically significant temporal cluster (LLR = 2,109.93, p < 0.001) from December 2013 to May 2015 was observed in all districts. Statistically significant spatiotemporal primary hot-spot was observed in 5 districts in different time periods.

Conclusion: Childhood diarrhoea was not distributed randomly over space and time, and showed an overall increasing trend of seasonal variation peaking between February and May.  The health departments and other stakeholders at various levels need to plan targeted interventional activities at hotspot seasons and areas to reduce morbidity and mortality.