 This randomized double-blind, placebo controlled trial RCT aims to evaluate the effect of oral administered E. coli phage in children aged 4-60 months of age with proven ETEC and EPEC diarrhea. Children will be screened to exclude V. cholerae infections by dark field microscopy, rotavirus by stool ELISA, and invasive diarrhoea clinically as well as by stool microscopy, to identify children with possible ETEC and EPEC diarrhoea. Enrolled children will be randomly assigned, in equal numbers, to receive either: i a new T4 phage cocktail or ii Russian anti-E. coli phage cocktail Microgen at the dose recommended by the manufacturer or iii only oral rehydration solution placebo for 5 days in addition to management of dehydration and continued feeding in accordance with WHO guidelines. Duration of diarrhea, daily and cumulative stool output, volume of oral rehydration solution intake, stool frequency, time to recovery and weight gain will be the main outcome measures. As the dose of phage we intend to use in this therapeutic trial is higher than the dose administered to young children in earlier safety trial, we plan to initially conduct a safety study with these three study products in 45 children with non cholera, non rotavirus and non invasive diarrhea, to randomize equally in the three intervention groups, as for the final study mentioned above. The outcome measures in this safety part will include assessment of laboratory parameters including renal and liver function tests, haematological indices, and microbiological efficacy of phage by measuring phage and E. coli titre in daily stool samples. If the higher dose is found safe, tolerable, and not associated with any significant adverse event, we will proceed to the clinical efficacy trial. 