Some microbiologists classify viruses as microorganisms, while others do not because they are "nonliving" and describe viruses as microscopic infective agents.
Viruses are unique microorganissms because
1.They cannot reproduce without a host cell
2.After contacting a host cell, a virus will insert genetic material into the host and take over that host is functions
3.The infected cell continues to reproduce more viral protein and genetic material instead of its usual products
This process that earns viruses the classification of "parasite