Virus replication. Computer artwork showing the replication of a virus (white) inside a host cell (red). All viruses need a host in order to replicate. The virus penetrates (upper left) the membrane and uses the cell's genetic processes to replicate its own genetic material (spirals) in order to duplicate itself. Thus, a large number of viral particles identical to the initial invader, develop inside the cell and erupt from it (upper right) when mature.