What do viruses require for their growth and reproduction?

Viruses only exhibit growth and reproduction within living cells, as they are obligate intracellular parasites. Unlike bacteria and other microorganisms, viruses do not have the cellular machinery needed for metabolism, energy production, or replication on their own. Instead, they invade a host cell and hijack its machinery to replicate their genetic material and produce new virus particles. This dependency on living cells makes them unique among pathogens, as they cannot grow or reproduce in any environment outside of a living host.

Other options, such as dead cells, specimen culture, or artificial media, do not provide the necessary living cellular context for viruses to replicate, as they lack the metabolic functions required for the viral life cycle. Therefore, the proper condition for viral growth and reproduction is solely found in living cells.