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Most bacteria responsible for enteric infections inhabit natural environments, but they are sparsely distributed. However, the eutrophication of environments due to increases in human population, human activities, and climate change stimulates bacterial propagation. The propagated bacteria can cause infection through consumption of water and food. Culture - including hygienic concepts, eating habits, ritual ceremonies, and other factors - can influence the frequency of contact between the bacteria and humans. Humans differ in their resistance to infection by the pathogenic bacteria due to differences in their immunity induced by past infections. Once infected, humans become “culture bottles of the pathogen” and bacteria propagated there are released into the environments. Political and economic activities such as the movement of labor harboring pathogens and the import/export of food contaminated with pathogens mediate the spread of infections. As such, we can look at the human-nature interaction through an analysis of the epidemiology of infectious diseases. Molecular epidemiological tools such as DNA fingerprinting can be a very powerful tool in the analysis, helping to prove in a objective manner the subjective hypothesis put forward in field study. The puzzles I have been collaborating with scientists in Asia to solve are infections caused by Vibrio parahaemolyticus, Vibriocholerae, and Escherichia coli O157.