Barry Marshall's and J. Robin Warren's (now "classic") letters to the Lancet in June 1983 suggesting that the, then unidentified, curved bacilli found in human gastric epithelia "may have a part to play in poorly understood, gastritis associated diseases (i.e. peptic ulcer and gastric cancer)" has deeply revolutionised the fields of Gastroenterology and Microbiology, causing an enormous impact on clinical management.1,2 The advent of Helicobacter pylori has brought about a complete revision of our concepts of chronic gastritis, peptic ulcer disease and even gastric cancer.3
Long before the culture of H pylori, spiral bacteria had been observed in the stomachs of a range of different animals. They were first reported in mammalian stomach just over 100 years ago.4,5 Since the isolation of H pylori by Warren and Marshal, gastric microbiology attracted world-wide attention and much information has accumulated on the basic bacteriology of H pylori.
The prevalence of H pylori in otherwise healthy individuals varies, depending mainly on age, education and income levels and country of origin. There are accumulating data suggesting that the major period of acquisition of infection is in childhood.6,7
The age of most frequent infection appears to be in person under 15 years of age, and perhaps in even younger children. The infection in children is mostly asymptomatic and not associated with specific clinical symptoms.8 Cohort studies in adults show acquisitions of about 0.3 to 0.5 per 100 person-years, in recent decades.6,7
H pylori infection is seen world-wide, while the frequency of associated illness is reported to vary. In India and Saudi Arabia, for example, the seroprevalence of H pylori in individuals over 50 years is higher than 80%, while in developed countries like England and France it is around 40%.6,7
The major risk factor for infection is the socio-economic status of the family during childhood. In a cross sectional study conducted over 3000 subjects, the EUROGAST Study Group concluded that subjects with higher education have considerably lower levels of infection (34.1%) compared with education up to the secondary level (46.9%) or those with primary education only (61.6%).9 As the socio-economic status of individuals and countries has risen, the prevalence in younger generations has declined.7 Thus, the age-related pattern of infection in developed countries can best be explained by the "cohort effect". Because successive generations have been less likely to become infected as children, these cohort show a lower frequency of infection in adults. This phenomenon seems to have preceded the introduction of antibiotics, although it may have been accelerated by their widespread use.3
It is difficult to address the association of infection and ethnicity independently of the confounding variables of subjects' and parents socio-economic status but a study in the USA showed that the prevalence may vary among different ethnic groups of similar socio-economic status.10
Variables such as gender, alcohol consumption, blood group and smoking do not seem to interfere in H pylori prevalence.6 Occupation may play a role in prevalence but the difficulty in choosing a comparison group makes it is very hard to exclude confounding variables (socio-economic and educational levels). Gastroenterologists and nurses were supposed to have higher prevalences but data are conflicting. 11-13
The transmission of H pylori seems to be mainly by person to person.6,7 Some reports have correlated H pylori infection with water supplies in Chile, Peru and Colombia but it is difficult to extrapolate from these...