Viruses depend on the host cells that they infect to reproduce. ... When it comes into contact with a host cell, a virus can insert its genetic material into its host, literally taking over the host's functions. An infected cell produces more viral protein and genetic material instead of its usual products.
Phages can generate the lytic cycle or the lysogenic cycle, although very few are able to carry out both. If lysis is carried out, lysogeny cannot be carried out and vice versa. In the lytic cycle, phage host cells are lysed (destroyed) after replication and encapsulation of viral particles, so that new viruses are free to carry out a new infection.