According to the World Health Organization (WHO) diarrhoeal disease is the second leading cause of death and causes high morbidity in children under five years old. Every year, around 525 000 children die of diarrhoeal disease. As diarrhoeal episodes usually follow the ingestion of contaminated food or water, children and individuals living in low- and middle-income countries are particularly at risk. It is estimated that currently about 780 million people lack access to improved drinking-water and 2.5 billion lack improved sanitation. The most common etiological agents of moderate-to-severe diarrhoea in in low-income countries are rotavirus and Escherichia coli.

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Other important pathogens include Cryptosporidium and Shigella species. Shigella and enterotoxigenic Escherichia coli (ETEC) account for about 200 million episodes of diarrhoea per year and are directly or indirectly responsible for about 107 500 annual deaths in children under 5-years of age. The African region and the South Eastern Asian region have the highest percentage of ETEC episodes, while most Shigella cases occur in the African region, Eastern Mediterranean region and Southern Asian region.