<unk>  is contagious, although the exact route of transmission is not known. Person-to-person transmission by either the oral–oral (kissing, mouth feeding) or fecal–oral route is most likely. Consistent with these transmission routes, the bacteria have been isolated from feces, saliva, and dental plaque of some infected people. Findings suggest<unk>  is more easily transmitted by gastric mucus than saliva. Transmission occurs mainly within families in developed nations, yet can also be acquired from the community in developing countries.<unk>  may also be transmitted orally by means of fecal matter through the ingestion of waste-tainted water, so a hygienic environment could help decrease the risk of<unk>  infection.
Helicobacter pylori
Giardia duodenalis
Entamoeba histolytica
Neisseria mucosa
Cryptosporidium parvum
Entamoeba gingivalis
Campylobacter upsaliensis
Ancylostoma duodenale