The term, “hepatitis” comes from “hepa” meaning “liver” and “itis” meaning “inflammation”. 
Viral infection is a common cause of acute (short duration) and chronic (long duration) hepatitis.
There are several forms of viral hepatitis. The most common are Hepatitis A, B and C, which are all caused by a different virus.
When hepatitis is present, the liver often becomes tender and enlarged and the patient usually has symptoms such as fever, weakness, nausea, vomiting, jaundice and loss of appetite. 
A lot of viruses can cause minor liver inflammation and Glandular Fever (Epstein Barr virus) can cause severe liver inflammation.
However, the Hepatitis A, B and C viruses predominantly affect the liver with other organ involvement being less obvious and less important.
Hepatitis can be due to non-viral infectious agents or to completely unrelated infections. Eg. Alcoholic Hepatitis.
The acquisition of hepatitis does not necessarily imply poor hygiene.