Oncogenic Viruses and Human Cancer: Molecular Mechanisms, Diagnostics, Vaccines and Therapeutic Advances

Abstract

Oncogenic viruses are preventable or therapeutically tractable causes of a substantial and geographically unequal fraction of human cancer. Their biological diversity, from small DNA viruses to retroviruses and non-integrating RNA viruses, has produced distinct tumour phenotypes but also revealed recurrent principles of carcinogenesis. This critical narrative review integrates evidence on high-risk human papillomaviruses, hepatitis B, C, and D viruses, Epstein–Barr virus, Kaposi sarcoma-associated herpesvirus, human T-cell leukaemia virus type 1, and Merkel cell polyomavirus. Human immunodeficiency virus is considered as an indirect carcinogenic cofactor through immune dysregulation, whereas human cytomegalovirus is treated as an unresolved candidate rather than an established tumour virus. Literature indexed through 2 June 2026 was selected from biomedical and scholarly databases, authoritative institutional sources, citation tracing, and DOI registries, with emphasis on causal evidence, mechanistic coherence, clinical validity, and translational relevance. The strongest shared mechanisms are persistent infection, dysregulated viral gene expression, interference with tumour suppressor and cell-cycle control, genomic or epigenomic instability, chronic inflammation, and immune escape. Yet the relative contribution of these processes differs markedly by virus, tissue, host immunity, and co-exposure. Diagnostics are most mature where viral biomarkers define tumour aetiology or enable screening, notably high-risk human papillomavirus testing, Epstein–Barr virus DNA in endemic nasopharyngeal carcinoma, and viral oncoprotein antibodies in selected Merkel cell carcinoma settings. Prophylactic vaccination has generated the clearest cancer-prevention evidence for human papillomavirus and hepatitis B virus, while elimination barriers, incomplete coverage, persistent post-cure risk, and the absence of licensed vaccines for several tumour viruses limit population impact. Immune checkpoint blockade and virus-specific cellular therapies demonstrate that viral antigens can be clinically actionable, but response heterogeneity and implementation complexity remain substantial. Progress now depends on harmonised viral attribution, prospective biomarker validation, prevention programmes designed for equity, and trials that integrate viral biology with tumour genomics and host immunity.