Viral disease — a difficult task for medicamentous therapy. The matter is that the virus can live and be reproduced only in the owner's cell, changing its exchange processes. Therefore long time was considered that it is impossible to influence viruses, without doing essential harm to an organism.
Over time this hypothesis was reconsidered. From the second half of the last century scientists develop antiviral drugs which affect different stages of a life cycle of a virus — interfere with attachment of a virus to a cell, penetration inside and to an exit of mature virus particles from a cell, break reproduction (replication).
Effect of these drugs in a therapeutic dose is pernicious for a virus and it is almost safe for an organism.