Viruses cause familiar infectious diseases such as influenza, rubella and warts. Multiple virus families exist and cause severe illnesses such as HIV/AIDS, hepatitis B and C and ebola. Viral diseases are a major health concern, with many people chronically infected. Some cancers are caused by viruses.
Antivirals are agents with the ability to either prevent viral infections or inhibit virus replication. As virus replication depends on host-cell machinery, many antiviral agents act on the key proteins involved in this process although antiviral drugs also target viral entry and modulation of the cellular defence system.
Some antivirals target components of the host cell and alter the ability of the virus to replicate efficiently, while others bind to the viral polymerase complex and restrict viral replication. RNA polymerase is essential for the replication of numerous RNA viruses.
Mechanisms of antiviral action include entry inhibitors of transcription, viral ribonuclease H, HBV surface antigen secretion, viral protease, RNA-dependent RNA polymerase, reverse transcriptase, viral neuraminidase, integrase strand transfer, DNA polymerase inhibitor and modulators of viral capsid assembly.