Established genetic polymorphisms in cagA and vacA genes affect H. pylori infection outcomes and also exhibit clear phylogeographical structural differences that reflect both ancient and recent human migrations and contacts [22], [26]. More generally, H. pylori is genetically highly diverse; independent isolates (from unrelated persons) are usually distinguishable from one another by DNA fingerprinting [27]; and strains typically differ from one another by some 2–5% in sequences of essential housekeeping genes and 5% or more in overall gene content [28], [29]. This stems from frequent point mutation, differences in restriction-modification systems, and recombination between divergent strains and species. H. pylori is transmitted preferentially within families and communities [30], and phylogenetically distinct sets of DNA sequences are found in strains from different parts of the world [26]–[29]