Lessons learnt from the epidemiology of Helicobacter pylori infection in Malaysia: JGHF Marshall and Warren Lecture 2017.

The study of Helicobacter pylori in Malaysia has given several important insights into the epidemiology of the infection and pathogenesis of disease. Malaysia has a multiracial Asian population with three major Asian races living together-Malay, Chinese, and Indian. Races remain fairly distinct because of a paucity of interracial marriages. The "Racial Cohort Hypothesis" proposes that the infection occurs within racial groups rather than between. As such, the high prevalence among Indians (> 50%) and Chinese (40-50%) reflects the high prevalence in their countries of origin even though migration had taken place more than two generations before. The Malays have a comparatively low prevalence of about 10-20%. Despite the high prevalence of H. pylori, the Indians have a low gastric cancer incidence of less than 10 per 100 000 per year. This is in contrast to the Chinese who has an incidence in excess of 20 per 100 000 per year. We have called this the "Indian Enigma." The reason for this enigma is unclear and is the result of interaction between bacterial virulence factors, host susceptibility, and environmental factors. Phylogenetically, Chinese bacterial strains are distinct from Indians and Malays and are predominantly hpEastAsia/hsp EAsia. CagA EPIYA motifs among Chinese belong predominantly to the more virulent ABD motif. There is no clear distinguishing profile among host genetic factors. Environmental factors particularly diet may play an important role. Indians consume chilies and curries, which may be gastro protective, whereas Chinese consume more preserved and salted foods, which are thought to be carcinogenic.