Transmission of H. pylori: The two possible routes of transmission are the person-to-person route and the waterborne route. The person-to-person route can be categorized into vertical transmission between mother and child and parallel transmission between non-mother and child. Parallel transmission routes include the fecal-oral route, the oral-oral route, and the gastro-oral route. 1. The fecal-oral route may be caused by H. pylori contaminating water and food after fecal excretion, and by feeding on contaminants through the mouth. 2. The -oral route may be due to the fact that H. pylori colonized in the oral cavity is transmitted to other people through the salivary intake, which may be related to the sharing of utensils, mothers chewing food to feed their young children, and other living habits. 3, – The oral route may be the typical mode of H. pylori infection in children. On the one hand, vomitus containing H. pylori can be used as a source of infection to infect new hosts. On the other hand, H. pylori can be colonized in the oral cavity through gastroesophageal reflux and vomiting, and H. pylori infected in the oral cavity can also develop into gastritis, which may be the reason for the high rate of eradication of H. pylori in the human gastric mucosa, but prone to recur (i.e., H. pylori not eradicated in the mouth re-enters and colonizes in the stomach). This may be the reason for the high rate of eradication of H. pylori from the human gastric mucosa, but it is easy to recur (i.e., H. pylori that is not eradicated from the oral cavity re-enters and colonizes the stomach). Drinking water containing H. pylori can also lead to H. pylori infection. The waterborne route of H. pylori transmission is supported by studies showing that H. pylori can survive for 10 days in river water at 4°C. However, there are also suggestions that the waterborne route can be used to spread H. pylori. However, it has also been argued that the concept of waterborne transmission is not valid, and that water is only a vehicle for human-to-human transmission of H. pylori.