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
WHO disease staging system for HIV infection and disease WHO disease staging system for HIV infection and disease WHO Disease Staging System for HIV Infection and Disease was first produced in 1990 by the World Health Organization and updated in September 2005. It is an approach for use in resource limited settings and is widely used in Africa and Asia and has been a useful research tool in studies of progression to symptomatic HIV disease. Most of these conditions are opportunistic infections that can be easily treated in healthy people. The staging system is different for adults and adolescents and children. Stage I: HIV disease is asymptomatic and not