Cheap and effective drugs called 'anthelmintics' are routinely administered to children in developing countries to eliminate infections by parasitic helminths. However, the effects of anthelmintic treatment on other pathogens (e.g., bacteria, viruses, protozoa) remain unknown. The aim of this study is to investigate the impact of anthelmintic treatment on the incidence of viral- and bacterial-induced diarrhea in school children in southern Vietnam. Diarrheal disease remains a substantial cause of morbidity and mortality in children in Vietnam, and these children are typically co-infected with intestinal helminths. As helminths and diarrheal pathogens infect the same intestinal niche, anthelmintic treatments may alter host immune responses and the composition of the gut microbiota in ways that affect infection and disease risks caused by diarrheal pathogens.