Fecal-oral route
The fecal–oral route (or alternatively the oral–fecal route or orofecal route) is a route of transmission of a disease, when pathogens in fecal particles passing from one host are introduced into the oral cavity of another host. One main cause of fecal-oral disease transmission in developing countries is lack of adequate sanitation and, often connected to that problem, water pollution with fecal material.
Background
The "F-diagram" explaining transmission routes and barriers was first proposed in a publication by Hesperian Foundation for the United Nations Development Programme (UNDP) in 2005. It has been widely used in many other sanitation publications since then. It was set up in a way that fecal-oral transmission pathways are shown to take place via nouns that start with the letter F: fingers, flies, fields, foods, and fluids (fluids stands here for polluted water - be it polluted drinking water, surface water or groundwater).
The F-diagram is also used to show how proper sanitation (in particular toilets, hygiene, handwashing) can act as effective barriers to stop transmission of diseases via fecal-oral pathways.