Contemplating the future without Helicobacter pylori and the dire consequences hypothesis.

Helicobacter pylori is a serious chronic transmissible pathogen that causes gastric structural and functional damage and is a major cause of morbidity and mortality worldwide. At least 20% of those infected will eventually experience a clinical outcome [1]. Table 1 shows the diseases in which H. pylori is a major cause. None are exclusive to the infection. The lifetime risk for an H. pylori-infected individual to develop peptic ulcer disease has been estimated at one in six, and 10–25% of those with peptic ulcers are expected to develop complications such as gastrointestinal hemorrhage or perforation. H. pylori infection is a necessary but not sufficient cause of gastric cancer. Gastric cancer is the second most common cancer worldwide. The lifetime risk of developing gastric cancer is related to the prevalence of H. pylori-associated atrophic gastritis and in high-risk countries is as high as 19.6% in Changle, China, and as low as 1.5% in the UK [2]. These differences reflect the variation in H. pylori prevalence, in strain virulence, and in host and particularly environmental factors [3]. Table 1 Diseases in which Helicobacter pylori infection is a major cause Primitive man was home to many intestinal parasites [4–8]. Improvements in the standards of living over the last several millennia and particularly the improvements in sanitation, availability of clean water, and better understanding of the practices of household hygiene have resulted in the disappearance of these previously common intestinal pathogens. H. pylori is one of the last major worldwide gut pathogens that has accompanied man on his many migrations [9,10]. The 19th century witnessed the appearance of a number of “new diseases” including paralytic polio, acute infectious hepatitis, and duodenal ulcer disease. In retrospect, the first two were related to major changes in sanitation that resulted in a change in the age of acquisition of polio virus and hepatitis A virus from infancy to young adulthood and the appearance of paralytic polio and acute infectious hepatitis as recognizable diseases. It is likely that this also marked the beginning of the loss of H. pylori as well as a change in the pattern of gastritis and the appearance of antral predominant gastritis. This change was enhanced by changes in standards of living and diet that resulted in the appearance of duodenal ulcer disease as another significant new disease. Duodenal ulcer was initially a disease of the upper classes as they could take the advantages of improved standards of living and improved diets. The improvements in household hygiene, sanitation, diet, and general standards of living led to a break in the chain of transmission of H. pylori such that the infection became increasingly less common among the middle and upper classes. Loss of the infection led to loss of duodenal ulcer disease that switched from being an upper-class problem to one of the lower classes where H. pylori was still common and for whom there was a trickle down of improved socioeconomic conditions. Further improvements in sanitation and household hygiene led to a continuing decline in H. pylori prevalence to where now the infection is present in only a small proportion of the upper and middle social classes in most Western societies.