Question

under what circumstances circumstances can virus reproduce

Answer 1

if they get a host which can provide them shelter and food then they can reproduce.

Answer 2

Viruses do not carry out respiration and they also do not grow orreproduce on their own. A virus needs a living cell in order toreproduce and this living cell in which the virus reproduces is called a host cell. Thus, viruses are small agents that can onlyreproduce inside a living cell of other organisms.
The structure of viruses allows them to succeed in their main mission—reproduction. Lytic Cycle Once attached to a host cell, a virus injects its nucleic acid into the cell. The nucleic acid takes over the normal operation of the host cell and produces multiple copies of the virus's protein coat and nucleic acid.