What are classified as noncellular submicroscopic pathogens?

Viruses are classified as noncellular submicroscopic pathogens because they do not possess the cellular structure that characterizes living organisms. Instead, viruses are made up of genetic material (either DNA or RNA) surrounded by a protein coat, and they require a host cell to replicate and propagate. Unlike fungi, bacteria, and yeasts, which are cellular organisms that can exist independently and perform metabolic functions on their own, viruses lack the machinery necessary for life outside of a host. This unique characteristic defines them as noncellular and highlights their status as obligate parasites that depend on living cells for reproduction.