Changes in human ecology and behavior in relation to the emergence of diarrheal diseases, including cholera.

Human populations throughout the world can be found in diverse conditions. A proportion of the population of developing countries lives in deprived conditions characterized by ramshackle housing, lack of piped water and sanitation, and widespread fecal contamination of the environment. Enteric infections, particularly due to bacterial pathogenes, are readily transmitted under these circumstances. In contrast, the majority of inhabitants of industrialized countries live in a sanitary environment that generally discourages the transmission of enteric pathogenes, particularly bacteria. In both these ecologic niches, changes in human ecology and behavior are leading to the emergence of certain enteric infections. Relevant factors in developing areas include urbanization (leading to periurban slums), diminished breastfeeding, and political upheaval that results in population migrations. In industrialized areas, large-scale food production (e.g., enormous poultry farms), distribution, and retailing (e.g., fast-food chains) create opportunities where widespread and extensive outbreaks of food-borne enteric infection can ensue if a breakdown in food hygiene occurs.