Drugs that are used to prevent or cure a disease caused by a virus, by interfering with the ability of the virus to multiply in number or spread from cell to cell.

Antivirals are drugs that kill or prevent the growth of viruses, including influenza. Tamiflu is an example of an antiviral drug used to treat influenza.

Antivirals (or anti-retrovirals) are drugs that interfere with the ability of HIV to replicate (or reproduce) itself in the body. For this reason, antiviral medications may help to slow down the progress of HIV infection, stop T-cells (white blood cells) from being destroyed and protect the immune system.