How is Helicobacter pylori (H. pylori) transmitted?

How Helicobacter pylori is Transmitted

H. pylori is transmitted primarily through person-to-person contact, most commonly via the fecal-oral route during episodes of diarrhea or the gastric-oral route during vomiting, with most infections acquired during childhood within families. 1, 2, 3

Primary Transmission Routes

Fecal-Oral Transmission

• The fecal-oral route appears to be the most common transmission pathway, particularly in developing countries with inadequate sanitation and contaminated water supplies. 2, 4
• H. pylori DNA has been detected in feces, supporting this route, though transmission is most efficient during episodes of diarrhea when bacterial shedding increases. 3, 4
• Waterborne transmission through fecal contamination represents an important source of infection, especially in regions with untreated water, with studies linking H. pylori infection to consumption of contaminated well water. 4, 5

Gastric-Oral (Vomitus) Transmission

• This route occurs primarily during episodes of vomiting when gastric contents containing H. pylori are expelled, facilitating person-to-person spread. 2, 3
• The gastric-oral pathway is particularly important in children and patients prone to vomiting. 2
• H. pylori DNA has been detected in vomitus, providing laboratory support for this transmission mechanism. 4

Oral-Oral Transmission

• While the oral-oral pathway through saliva or dental plaque is possible, the evidence does not support that this route is universal or predominant. 2
• H. pylori DNA has been detected in saliva and dental plaque, but the viability and infectivity of organisms in these sites remains uncertain. 4

Key Transmission Patterns

Intrafamilial Transmission

• Intrafamilial clustering is well-documented, with family members of infected patients at significantly elevated risk. 1
• Person-to-person transmission within families represents the dominant pattern in developed countries, with infections typically acquired during childhood from parents or siblings. 1, 4, 5
• Family members residing in the same household as patients with proven active H. pylori infections warrant testing. 1
• Testing and treating all infected family members protects other household members from infection and reinfection. 1

Environmental and Socioeconomic Factors

• Inadequate sanitation, crowded living conditions, lack of indoor plumbing, and limited access to clean water strongly facilitate transmission. 6, 7, 4
• The prevalence has steadily declined in affluent countries due to improvements in sanitation, standards of living, and housing infrastructure. 6, 7
• Poor hygiene practices, unsanitary food preparation, and food exposed to contaminated water or soil increase transmission risk. 4, 5

High-Risk Populations

• First-generation immigrants from high-prevalence areas (Central and South America, Caribbean, Eastern Europe, Asia, India) serve as reservoirs and maintain elevated infection risk. 6, 7
• Specific ethnic groups in the United States (Native Americans, blacks, Hispanics) show 2.6 to 3.2-fold higher prevalence. 1, 7
• First-degree relatives of gastric cancer patients should be tested due to intrafamilial transmission patterns. 1

Important Clinical Caveats

• Iatrogenic transmission following endoscopy is the only proven mode of transmission with direct evidence, highlighting the importance of proper endoscope disinfection. 4
• The anal-oral and genital-oral routes remain hypothetical without substantial supporting evidence. 2
• Animal-to-human transmission (zoonotic) has not been definitively established, though sheep and domestic cats have been investigated as potential reservoirs without conclusive evidence. 4
• Foodborne transmission may be more important in rural developing areas compared to urban developed regions where within-family transmission dominates. 5
• Multiple transmission pathways likely operate simultaneously, with the predominant route varying by geographic region, socioeconomic conditions, and age of exposure. 2, 8