GI Epidemiology: infection epidemiology and acute gastrointestinal infections

BACKGROUND: Gastrointestinal infection is a major cause of morbidity and mortality worldwide. The World Health Organisation estimated that in 2001 diarrheal disease was the third most common cause of mortality from infectious diseases worldwide, accounting for some 1.9 million deaths. Gastrointestinal infection is also linked to chronic diseases, for example Helicobacter pylori infection and gastric cancer. AIM: To introduce the features of infection epidemiology that differentiates it from disease epidemiology in general. CONCLUSION: The epidemiologic study of infection is essential for disease control. Infection epidemiology requires consideration of micro-organisms (the infection process and transmission pathways) as well as the host (clinical presentation, behavior and immune status). Although infection epidemiologists often draw on methods used in chronic disease epidemiology there are some special features of infection epidemiology that require additional investigative approaches. We have highlighted these unique features and described some of the special methods available to track infection to its source. KEY POINTS: * The epidemiologic approach to the investigation of gastrointestinal infection is influenced by the interaction between micro-organisms and the host. * The infection epidemiologist can draw on "standard" epidemiologic techniques and on special methods. * Collaboration with microbiologists is essential for studying infection epidemiology. The purpose of this chapter is to introduce the features of infection epidemiology that differentiate it from disease epidemiology in general. Epidemiologic concepts covered in other chapters will not be repeated here, but readers should bear in mind that those methods are also available to use in the study of infection.