Yuichiro Noiri

Helicobacter pylori is found in the stomach, which is its optimal habitat, and is considered an important factor in various serious diseases, including stomach cancer. The World Health Organization has identified H. pylori as a causative agent of gastric cancer, as confirmed by animal experiments in rodents. The fact that H. pylori can live in the harsh environment of stomach acid was the greatest hindrance to the discovery of H. pylori . It was not so long ago, in 1983, that it was successfully isolated and cultured. Subsequently, H. pylori eradication therapy was established, and it became possible to control gastric cancer to some extent. However, the mechanism, route, and mode of H. pylori infection still remain unclear. Furthermore, currently, the prevention of first‐episode gastric cancer and control of recurrent gastric cancer are not perfect. One of the reasons for this may be that the status of H. pylori in the oral cavity, which is the entry point for the organism (the beginning of the digestive system: the first route of infection), is still unknown. Therefore, we reviewed the current status of H. pylori infection in the stomach and oral cavity, focusing on (1) the mechanism of infection, (2) pathogenic factors, (3) the actual status of eradication therapy, and (4) control strategies.