Virology is the branch of science that specifically studies viruses, which are microscopic infectious agents that can only replicate inside living host cells. Unlike bacteria, fungi, or parasites, viruses lack cellular structure and require a host for reproduction. Understanding viruses is crucial for diagnosing, preventing, and treating viral infections. This specialization focuses on viral structure, genetics, pathogenesis, and the immune response to viral infections, making it distinct from microbiology branches that study other microorganisms.

Reference: Medical Microbiology, Murray et al., 9th Edition.