Causes of H. pylori Infection
H. pylori infection is caused by transmission of the bacterium Helicobacter pylori from person to person, primarily through oral-oral or fecal-oral routes, with acquisition typically occurring in childhood and strongly linked to poor hygiene, crowded living conditions, and low socioeconomic status. 1, 2
Primary Transmission Routes
Person-to-person transmission is the most likely mode of H. pylori spread in the general population, occurring through:
- Oral-oral route: Transmission via vomitus or possibly saliva, with H. pylori DNA detected in saliva, dental plaque, and gastric juice 1
- Fecal-oral route: Transmission through contaminated feces, with H. pylori DNA detected in stool samples 1
- Iatrogenic transmission: The only proven mode of transmission, occurring through contaminated endoscopy equipment 1
Environmental and Social Risk Factors
The level of H. pylori contamination depends heavily on familial and environmental context:
- Poor hygiene and inadequate sanitation practices are strongly associated with higher infection prevalence 1, 2
- Crowded or high-density living conditions facilitate transmission among family members, with evidence of intrafamilial clustering 1, 2
- Low socioeconomic status is the main risk factor for H. pylori infection, especially among children 2
- Contaminated water sources: Waterborne transmission through fecal contamination is an important source, particularly in areas with untreated water, with studies linking H. pylori infection to contaminated well water consumption 1
- Food prepared under less than ideal conditions or exposed to contaminated water or soil increases infection risk 1
Timing and Geographic Patterns
- Childhood acquisition: Most infections occur during childhood, with earlier acquisition in developing countries and populations of low socioeconomic status 1, 3
- Geographic variation: Infection rates are higher in developing than developed countries, with prevalence declining in Western industrialized nations but plateauing at high levels in developing and newly industrialized countries 2, 4
- Immigrant populations: Infection status remains high in immigrants from countries with high H. pylori prevalence 2
Protective Factors
- Adequate nutritional status, especially frequent consumption of fruits and vegetables and vitamin C, appears to protect against H. pylori infection 1
- Improved hygiene practices correlate with decreasing infection rates in developed countries 1
Important Clinical Context
H. pylori is a human-specific pathogen with humans serving as the principal reservoir, affecting approximately 50% of the world's population 1. The bacterium causes chronic gastritis in all infected individuals and is responsible for 71-95% of all gastric cancer cases 5. Understanding transmission routes is critical because recurrent infection after successful eradication suggests ongoing intrafamilial exposure, warranting testing and treatment of household members 6.