Effects of infection in gastrointestinal tract malignant diseases: From the oral cavity to rectum.

() has infected approximately fifty percent of humans for a long period of time. However, improvements in the public health environment have led to a decreased chance of infection. However, a high infection rate is noted in populations with a high incidence rate of gastric cancer (GC). The worldwide fraction of GC attributable to is greater than 85%, and a high prevalence is noted in gastric mucosa-associated lymphoid tissue lymphoma patients. These results indicate that the majority of GC cases can be prevented if infection is eliminated. Because exhibits oral-oral or fecal-oral transmission, the relationship between this microorganism and other digestive tract malignant diseases has also attracted attention. This review article provides an overview of and the condition of the whole gastrointestinal tract environment to further understand the correlation between the pathogen and the host, thus allowing improved realization of disease presentation.