Technically viruses are not living as they do not contain any of the membrane bound organelles (mitochondrion) as well as ribosomes, which are present in cellular life forms; viruses contain nucleic acid (either DNA or RNA). All antibiotics invariably act by interfering with the prokaryotic 70S ribosomes during protein synthesis; but antibiotic has no effect on the eukayotic 80S ribosomes. So during viral infection, when person’s general immunity is low they are prone to infection by prokaryotic organisms (eg Staphylococcus aureus); a course of treatment with antibiotics kills the infecting bacterium, unless it happens to be resistant to that antibiotics – eg Methicillin-resistant Staphylococcus aureus, (MRSA) a common hospital bug.
in virus, the genetic material are so easy to rearrangement to produce new specific epitops (Antigens) which have the ability to evade the immune system. this phenomena called genetic shift and/or drift depending on the species of viruses that integrated with each other in genetic material
The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids pieces of DNA that can move between cells while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity. Viruses are considered by some to be a life form, because they carry genetic material, reproduce, and evolve through natural selection. However they lack key characteristics that are generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life.
Immune responses can also be produced by vaccines, which confer an artificially acquired immunity to the specific viral infection
Microbes are already ruling the world, in practically every niche. We have more microbes living in our body than our own signature cells. All multicellular beings are like preserved food of microbes and shall finally be consigned to microbes.