The Human Virome in Infectious Diseases: Insights from Chronic and Acute Infections Across Body Sites-A Narrative Review.

The human virome, comprising eukaryotic viruses, bacteriophages, and viral genetic material, is a dynamic component of the microbiome with growing relevance in infectious diseases. This narrative review is structured to: (i) summarize the general composition of the human virome and methodological challenges, including the fraction of unclassified viral "dark matter"; (ii) describe virome alterations in chronic infections; and (iii) explore site-specific virome dynamics across respiratory, intestinal, and genito-urinary tracts in both chronic and acute infections. In chronic viral infections such as HIV, HBV, HCV, and HPV, a recurrent feature is the expansion of Anelloviridae-particularly torque teno virus-reflecting impaired immune surveillance rather than direct pathogenicity, suggesting their potential as surrogate biomarkers of immune competence. Evidence on virome changes in chronic bacterial and parasitic infections remains limited, highlighting a critical knowledge gap. Acute infections are associated with compartment-specific shifts in eukaryotic viruses and bacteriophage communities, often paralleling changes in bacterial populations and inflammatory responses, with implications for disease severity. Despite advances in metagenomic approaches, a substantial proportion of viral sequences remains unclassified, limiting functional interpretation. Nevertheless, virome profiling provides an ecosystem-level perspective, offering insights beyond single-pathogen detection and supporting emerging applications in diagnostics, immune monitoring, prognosis, and infectious disease surveillance.