The reasoning: epidemiology
Diarrhoea remains among the leading causes of under‑5 deaths in India. Agents: rotavirus (the leading cause of severe dehydrating diarrhoea in infants before vaccine introduction), norovirus, ETEC, Shigella, Campylobacter, V. cholerae, Cryptosporidium, Giardia. Risk factors: unsafe water, poor sanitation, no handwashing, non‑exclusive breastfeeding, malnutrition, vitamin A and zinc deficiency, measles, unsafe food storage, bottle feeding. Vicious cycle: diarrhoea ↔ malnutrition (environmental enteropathy).