Hepatitis B and hepatitis C viruses: a review of viral genomes, viral induced host immune responses, genotypic distributions and worldwide epidemiology

Hepatitis B and hepatitis C viruses (HCV) are frequently propagating blood borne pathogens in\udglobal community. Viral hepatitis is primarily associated with severe health complications,\udsuch as liver cirrhosis, hepatocellular carcinoma, hepatic fibrosis and steatosis. A literature\udreview was conducted on hepatitis B virus (HBV), HBV genome, genotypic distribution and global\udepidemiology of HBV, HCV, HCV genome, HCV and host immune responses, HCV genotypic\uddistribution and global epidemiology. The valued information was subjected for review. HBV has\udstrict tissue tropism to liver. The virus infecting hepatocytes produces large amount of hepatitis\udB surface antigen particles which lack the DNA. It has capability to integrate into host genome.\udIt has been found that genotype C is most emerging genotype associated with more severe liver\uddiseases (cirrhosis). The approximate prevalence rate of genotype C is 27.7% which represents\uda major threat to future generations. Approximately 8% of population is chronic carrier of HBV\udin developing countries. The chronic carrier rate of HBV is 2%-7% in Middle East, Eastern and\udSouthern Europe, South America and Japan. Among HCV infected individuals, 15% usually have\udnatural tendency to overcome acute viral infection, where as 85% of individuals were unable to\udcontrol HCV infection. The internal ribosomal entry site contains highly conserved structures\udimportant for binding and appropriate positioning of viral genome inside the host cell. HCV infects\udonly in 1%-10% of hepatocytes, but production of tumor necrosis factor alpha (from CD8+ cells) and\udinterferon-gamma cause destruction of both infected cells and non-infected surrounding cells.\udAlmost 11 genotypes and above 100 subtypes of HCV exists worldwide with different geographical\uddistribution. Many efforts are still needed to minimize global burden of these infections. For the\udcomplete eradication of HBV (just like small pox and polio) via vaccination strategies, sincere\udefforts would be required from government and nongovernmental organizations