The role of epidemiology in understanding the health effects of Helicobacter pylori

Helicobacter pylori infects one-half or more of the world population and ca uses chronic gastritis, peptic ulcer, and probably gastric cancer as well. The public-health impact of this infection is far from trivial. Chronic gas tritis and peptic ulcer disease are common across populations. Gastric canc er rates have declined during this century, but this cancer remains second among causes of cancer deaths worldwide. Much has been learned about biolog ical and clinical aspects of H. pylori, but key epidemiologic questions hav e not been answered. How infection results in diverse diseases, the precise modes of transmission, and a comprehensive solution to H. pylori as a publ ic-health problem remain elusive. In this paper, we highlight methodologic challenges and outline an agenda for future research. Challenges include im proving validation of detection methods and considering the limitations of these methods when interpreting epidemiologic data. The role of cofactors i n H. pylori-induced diseases requires extensive exploration. Many intriguin g areas of H, pylori research require the skills of epidemiologists. The di scovery of an infectious etiology of common chronic diseases presents a pro mising opportunity for improving public health.