Final answer:
The formation of mature viruses occurs in the assembly stage of the virus replication cycle, which is followed by the release of the viruses to infect new cells. The cell does not necessarily die immediately during virus release.
Step-by-step explanation:
The formation of mature viruses occurs during the assembly stage of the virus replication cycle. This stage comes after the virus has attached to a host cell, penetrated the cell membrane, and replicated its genetic material. In the assembly phase, the newly formed viral components, such as capsid proteins and viral genetic material, are assembled into complete virions. The next step is the release of these mature viruses, whereby they exit the host cell and are able to infect adjacent cells, continuing the replication cycle.
It is a common misconception that the host cell dies immediately during the budding process; however, the cell does not necessarily undergo lysis and can remain alive for a period of time, although it may be damaged and unable to function normally. The final release of the viruses can occur through lysis, in the case of the lytic cycle, where the virus replicates and bursts out of the cell, or through budding, especially seen in animal viruses, where viruses exit the cell individually and the host cell may survive for some time post virus release.