Epidemiology, Risk Factors, ivnestigations Managmeet and Prevention of Hepatitis C Virus infection

Abstract

In 1970s hepatitis A virus (HAV) and hepatitis B virus (HBV) were identified. However there remained quite a number of cases of viral hepatitis which were not due to hepatitis A, B, cytomegalo or Ebstien Barr virusses and the term non A non B htpatpits wwas used to describe such cases. The disorder accounted for 75 - 90% of transfusion induced hepatitis but it also included enterically transmitted, sporadic, endemic and community acquired disease. in 1989, by using molecular biological techniques, the 20 years search for the baffing agent responsible for this disease culminated in the identification of the hepatitis C virus (HCV). HCV is a member of the flaviviridae family, which includes yellow fever and Dengue viruses. It has a positive single stranded RNA genome which encodes a nucleocapsid proteins. Nucleotide sequence variation and cloning of RNA has confirmed the heterogeneity of HCV leading to its classification into genotypes. The variabitlity of HCV is such as to suggest a two tier classficiation into types and subtypes. the known types are numbered from 1 and the sugbtypes a b and c in order of discovery. The current system of nomenclature includes 6 major genetic types and upto 40 different recognized subtypes. Type 1a, 1b, 2a, 2b and 3a are common in western Europe and USA. Type 1b, 2 and 2b in China and Japan type 3 in Thailand, singapore, Bangladesh and India, Type 4 in Middle East and Centra Africa and Type 5 in South Africa.