Viruses are infections agents that are capable of replicating only when inside the living cell of living organisms. Diseases such as influenza, measles, mumps, SARS, AIDS, and Chicken pox are caused by viruses. The compounds in clinical use today combat viruses by acting on key stages of the viral cycle or the interfere with the genetic material of the viruses. Currently, most of these drugs are designed to help deal with HIV, herpes viruses, the hepatitis B and C viruses, and influenza A and B viruses. At present, there are fewer drugs to treat infections of RNA viruses Compared to DNA viruses.