Hepaciviruses

Hepaciviruses constitute a genus within the family Flaviviridae. They are enveloped, single‑stranded, positive‑sense RNA viruses that primarily infect mammalian hosts. The most clinically relevant species, Hepatitis C virus (HCV), causes chronic liver disease worldwide.

The genome is approximately 9.6 kilobases and encodes a single polyprotein that is processed into structural proteins (core, E1, and E2) and non‑structural proteins essential for replication. Genetic diversity is characterized by seven major genetic genotypes (1–7) and numerous subtypes that differ in geographical distribution and treatment response.

Transmission occurs mainly through exposure to infected blood, including transfusion, dialysis, tattooing, and syringe sharing. In some regions, vertical transmission from mother to child and percutaneous routes also contribute. The virus exhibits high cellular tropism for hepatocytes but can infect extra‑hepatic tissues such as renal tubular epithelial cells and lymphoid cells.

Acute infection is often asymptomatic, whereas chronic infection leads to progressive hepatitis, cirrhosis, and hepatocellular carcinoma. Viral replication induces an inflammatory response that damages liver tissue, and immune escape mechanisms limit clearance by the adaptive immune response.

Diagnosis relies on serology for HCV antibodies and nucleic acid testing for viral RNA. Direct‑acting antiviral agents target the NS3/4A protease, NS5A, and NS5B polymerase, achieving sustained virologic response rates above 95%. No effective vaccine currently exists.

Research focuses on vaccine development, novel antiviral targets, and strategies to address drug resistance. Public health measures emphasize screening of blood products, harm‑reduction programs, and education to reduce transmission, thereby decreasing the global burden of hepacivirus infection.