Vectors for the transmission of Helicobacter pylori

Abstract

H. pylori is strongly associated with gastroduodenal disease, including chronic active gastritis, duodenal ulcer, and gastric adenocarcinoma¹. The seroepidemiology of H. pylori has been studied extensively in the United States and in other countries². In developing countries almost all children are infected by age 11, whereas in developed countries infection is much less common and predominantly seen in children of lower socioeconomic circumstance. This high frequency of seropositivity and acquisition of the infection during infancy are characteristic of disadvantaged socioeconomic groups living in crowded or poor hygienic conditions, and appears to be independent of gender and ethnic origin³. In Western countries, longitudinal studies indicate that the high frequency of seropositivity in older adults might be due to a higher rate of H. pylori infection in the years between the two world wars when that population was in childhood, than during recent years (cohort effect)⁴. For instance, in Japan the prevalence is around 80-90% for those aged 40-49 years or older, born before 1950. After World War II, prevalence dropped to 45% for those born between 1950 and 1960, 25% for those born between 1960 and 1970, and 20% for those born between 1970 and 1980⁵. The nearly 4-fold decline in prevalence has been attributed to the postwar economic development that led to improved sanitation and living conditions.