Infectious GI diseases are an increasingly serious problem world-wide, exacerbated by high population densities, rapid and extensive population movements, deteriorating water quality and intensive farming methods, which increase the contamination of food, transmission of infectious agents and the development of antibiotic resistance.

Oro-faecal contamination is the principal route of transmission, with food or water being the vectors

Poor hygeine, contamination (see Hong Kong's wet market butchers to understand how this might be the case). Hong Kong has had a number of recent infectious disease outbreaks related to poor food hygeine, and annually has several cases of typhoid and cholera related to this.