The transmission route is still not fully understood, Hp is parasitic in humans, but as experimental animals such as Mongolian gerbils, pigs, cats and civets can also be infected by Hp, there are reports that Hp can be isolated from these animals, but most studies believe that in the natural environment, human is the only source of infection, human-to-human transmission is the only transmission route, whether through fecal-oral, oral-oral, gastric-oral transmission or other routes is still controversial. -However, most studies have concluded that humans are the only source of infection in the natural environment and that human-to-human transmission is the only route of transmission. In a domestic survey of 150 couples (average 6.5 years of marriage) with Hp infection, it was found that 78.94% of one spouse with Hp (ten) had Hp (ten); while 20% of the spouses of one spouse with Hp (one) had Hp positivity, suggesting the existence of family aggregation of Hp infection. An epidemiological survey in Guangzhou showed that residential density and infection rate were closely related, suggesting that close contact increases the chance of transmission, which is consistent with the findings of family aggregation. A domestic group reported that the Hp infection rate among the whole family members of Hp-positive children who were prevalent was 68.8%, and the infection rate of both parents was 63.6%, while the difference was 15.4% and 22.2% in the families of Hp-negative prevalent children, respectively, which was very significant. In foreign countries, the infection rate of children with both parents infected with Hp was 44%, which decreased to 30% if only one parent was positive and 21% if both parents were negative, with a significant difference, in which the mother had a greater impact, with a risk factor of 16.5 for children with Hp-positive mother and only 3.8 for positive father. The difference was even more significant, as 85% of the children were infected if one or both parents were Hp positive and only 22% if both were negative. Investigation of mutual transmission between siblings showed that if there are 1~4 siblings in the family, the risk of children being infected increases to 1.5~4.3; if these 1~4 people have Hp infection, the OR value is even greater to 1.5~7.1, indicating that close contact with each other increases the possibility of transmission. Further studies showed that family members were mostly infected with the same subgroup of Hp. The basis for supporting fecal-oral transmission is that the epithelium of the gastric mucosa is rapidly renewed and shed, and the Hp residing on it must be shed and discharged from the feces through the gastrointestinal tract, contaminating food and water sources to spread the infection. Hp has been isolated from gastric juice and cultured in the stool of patients with diarrhea and gastric acid deficiency, and isolation of Hp from the natural environment is also evidence of fecal-oral transmission, and successful isolation of Hp from ditch water in South American countries has been reported. However, some studies have shown that Hp cannot multiply in milk and tap water, but can survive for about 10 and 4 days and turn into spherical bacteria. Normal human duodenal fluid has a strong bactericidal effect on Hp, and it is generally impossible for Hp to survive in the feces through this barrier. Support for oral-oral and gastric-oral transmission is based on the fact that Hp shed with gastric epithelial cells can survive in gastric juice, enter the oral cavity through gastroesophageal reflux, lodge in dental plaque, and spread the infection through saliva. Hp detection from saliva, regurgitated vomit, and dental plaque has been reported, mostly using the multiplex enzyme chain reaction (PCR) method, with some reports of successful culture, but not yet reproducible and recognized. Most of the studies using PCR method used only one set of primers, which cannot yet exclude the cross-reactivity of oral miscellaneous bacteria, such as the use of two sets of primers, the positive rate is greatly reduced, so that the specificity of the PCR method is in doubt. Pakistan reported 173/178 (97%) positive tartar smears and urease tests in the Hp-infected population without brushing habits, compared to 7/30 (23%) in controls with brushing habits. A West African group reported a 2.9-fold risk factor for Hp infection in young children whose mothers fed them by chewing food and then comparing them to non-chewing fed controls. To summarize the above, under natural conditions, Hp is transmitted through human-human transmission, while transmission through animals, pets, flies, and insects has not been demonstrated, if at all, and is an isolated phenomenon. Transmission through medical sources has received much attention, with gastroscopy being an important way to cause medical transmission of Hp. After examination of Hp-positive patients, 61% of gastroscopic surfaces and internal tracts were found to be contaminated with Hp by PCR, and biopsy clamp contamination was more severe. A study using DNA fingerprinting confirmed that gastroscopy contamination caused Hp infection in 2 patients, and a Dutch group of 281 Hp-negative patients prospectively observed Hp infection after microscopy in 3 cases (1.1%). Japanese scholars observed that 420 cases (0.02%) of 1913939 gastroscopies had acute gastric mucosal lesions within about 1 week after the examination, and these patients were seronegative for Hp antibodies before the microscopy, and more than half of them turned positive after the microscopy, so the lesions were thought to be caused by acute Hp infection caused by the endoscope, so the endoscope should be thoroughly disinfected by physical and chemical methods. Other areas that can cause medical transmission of Hp include dentistry and pediatric infant rooms. China is a high prevalence area for Hp infection and medical transmission may be more common. Table 2-1 Risk factors for Hp infection Poor economic status Low educational level Crowded housing Poor sanitation Contaminated water or food Exposure to Hp-infected persons Gastroenterologist Nurse Co-habiting family members with Hp infection