Human digestive system digestive system is subject to a wide range of disorders many of which can be congenital. Mouth diseases can also be caused by pathogenic bacteria, viruses, fungi and as a side effect of some medications. Mouth diseases include tongue diseases and salivary gland diseases. A common gum disease in the mouth is gingivitis which is caused by bacteria in plaque. The most common viral infection of the mouth is gingivostomatitis caused by herpes simplex. A common fungal infection is candidiasis commonly known as "thrush" which affects the mucous membranes of the mouth. There are a number of esophageal diseases such
Human virome cells and material in our gut also carry viruses. When viruses cause harm by infecting the cells in the body, a symptomatic disease may develop. Contrary to common belief, harmful viruses may be in the minority compared to benign viruses in the human body. It is much harder to identify viruses than it is to identify bacteria, therefore our understanding of benign viruses in the human body is very rudimentary. The health effects of viruses on an individual are dependent on the individual's immune system. Recent research has linked the emerging idea of the hygiene hypothesis to viruses. This hypothesis