Transmission of Helicobacter pylori

Helicobacter gastroduodenitis is a serious chronic infectious disease that is responsible for widespread morbidity and mortality. An understanding of the way in which it spreads is fundamentally important when considering measures for its control. Its prevalence is highest in the developing world and in individuals with a disadvantaged socio-economic childhood. The disease is believed to be contracted during the early years of life. A faeco-oral mode of transmission is considered by many to be the most likely mode of spread, however, the organism is difficult to culture both from faeces and from the environment and unlike other enteric organisms Helicobacter does not give rise to a diarrhoeal illness that would facilitate its transmission. An orooral route of spread has also been suggested, however, Helicobacter cannot be cultured from saliva, and if it was spread orally there is no reason why childhood should be the most frequent age for its acquisition. A third possibility is that the bacterium is transmitted gastro-orally. In favor of this hypothesis, the infection is easily acquired following gastric intubation with inadequately disinfected equipment. Children have a greater tendency to vomit than adults, and tend to explore with their fingers and place foreign objects in their mouths. Initial Helicobacter infection causes a dyspeptic illness characterised by mucousy vomiting, which may provide a vehicle for transmission. Furthermore, during the acute infection the organism induces achlorhydria in the host, possibly enabling the organism to survive longer in vomited mucus in the absence of acid. This theory fits best with the epidemiological data. Those most at risk are children living in an overcrowded environment who share beds with one another and live in houses that do not possess a fixed hot water supply (thus making cleaning up of vomit more difficult). It is also commoner in institutionalized children and is associated with school catchment areas.