Viral diseases, world incidence

Viral hepatitis can occur at any age and is the most common cause of liver disease in the world. The true prevalence and incidence may be underreported because most patients are asymptomatic. The epidemiology, etiology, and pathogenesis vary depending on the type of hepatitis and will be considered separately below. 

Parkinson s disease is primarily a disease of older people, although it can result as a consequence of brain injury or viral infection. Environmental exposure to some toxins may also be a cause. Incidence increases with age from very low in 60-year-olds to around 50% of people in their nineties. The incidence of Parkinson s disease is approximately 1 1000 in the general population, rising to 1 100 over the age 65 and 1 50 over the age of 80. There are more than 120 000 people with Parkinson s disease in the UK and it is common in all parts of the world. 

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