‘Viral
hepatitis’ refers to a primary infection or inflammation of the liver by any
one of a heterogenous group of hepatitis
viruses which consists of types A, B, C, D, E and G. Hepatitis viruses are
taxonomically unrelated. All the human hepatitis viruses are RNA viruses except
for HBV, which is a DNA virus. The features common to them are their
hepatotropism and ability to cause a similar icteric illness, ranging in
severity.
The
most common viral hepatitis is hepatitis A, formerly called infectious
hepatitis, caused by hepatitis A virus (HAV), a single stranded RNA virus
usually transmitted by the faecal-oral route. Hepatitis B, formerly
called serum hepatitis, is caused by the hepatitis B virus(HBV), a
double stranded DNA virus usually transmitted via blood. Hepatitis C,
formerly called non-A non-B (NANB) hepatitis. Hepatitis E, (HEV)
transmitted by the faecal-route and formerly called non-A non-B non-C
hepatitis. An especially severe form of the disease hepatitis D or
delta hepatitis, is caused by the presence of both hepatitis D virus (HDV) and
HBV.
