In all instances it is viral proteins that are responsible for this third and final stage although host proteins and other factors may still associate with the virus particle. Genome replication has been initiated but progeny virus have not yet formed. There is then a maturation phase when viral material accumulates exponentially in the cell or surrounding medium. After a few hours cells infected with lytic viruses become metabolically disordered and then die, viral production ceases. Titres then slowly drop.
Cells infected with non lytic viruses can continue to produce viral particles indefinitely.
This reproductive cycle lasts less than an hour with many bacteriophage, 6-8hrs in picornaviridae and more than 40 hrs in herpesviridae. Cells infected with polio virus can yield more than 100000 copies of virus per infected cell. Thereafter virus production stops but the genome remains present in the cell, examples include Epstein Barr Virus and herpes simplex virus. This kind of infection may still have serious consequences e.g cell transformation and cancer. Chapter 4 of Principles of Molecular Virology Provides an essential introduction to modern virology.