Epidemiology of H. pylori Infection
from: Helicobacter pylori (Edited by: Lyudmila Boyanova). Caister Academic Press, U.K. (2011)
H. pylori causes the second most common chronic bacterial infection in humans. As a result of the childhood-acquired and usually life-long (unless eradicated) infection, about 12-24% of the H. pylori positive subjects develop severe diseases e.g. peptic ulcers or gastric malignancy. In developed countries, the infection usually spreads intrafamilially; however, in developing countries or underdeveloped rural areas, it can be acquired often extrafamilially or via environmental contamination, leading to higher infection prevalence and greater intrafamilial diversity of the strains there. Infected mother and older siblings are important factors for H. pylori transmission to children. The transmission routes are oral-oral (by saliva), which prevails in the developed world, faecal-oral (person-to-person or by contaminated water, or maybe food), mainly in the developing countries or gastro-oral (by vomiting and regurgitation). Role of viable but not culturable coccoid forms and biofilms appears to be important. Oral H. pylori seems to be associated with combined oral and gastric infections, probably more often in the developing countries. However, PCR accuracy for detection of extra-gastric H. pylori needs improvement. As a whole, the infection prevalence is still high in countries/groups with poor socio-economic status. In many developing countries, ≥50% of children and ≥70% of adults have been H. pylori positive vs. only <15% of children and ≤20-40% of adults in most developed countries. Detection of anti-CagA antibodies has been used to spot infections by virulent strains and the importance of East Asian CagA testing has been stressed. Both reinfection and infection clearance also have been reported, mainly in children, although in high-prevalence countries, the infection clearance is unimportant. Many risk factors for the infection mirror poor socioeconomic status and a strong birth cohort effect. Both dietary and environmental factors are likely to modify the infection prevalence and should be further evaluated. In brief, improved hygiene and living conditions, urbanisation and growing antibiotic use for H. pylori and many other infections, all have led to a decrease in both infection and reinfection rates in the developed countries and, already, in some developing countries. However, the infection still affects every second person worldwide. Moreover, many important questions on the infection transmission routes and reservoirs still need elucidation read more ...