Can Oncogenic Animal Viruses Pose a Threat to Humans?

Oncogenic viruses are well-established contributors to cancer development in both humans and animals. While many animal oncogenic viruses exhibit strong host specificity, concerns remain about their potential to cross species barriers and impact human health. This article examines the classification and molecular mechanisms of oncogenic viruses, including retroviruses, papillomaviruses, herpesviruses, and hepadnaviruses, in animals. It explores historical cases of cross-species transmission, such as the contamination of early polio vaccines with simian virus 40 (SV40), which resulted from the use of rhesus monkey kidney cells and insufficient screening for latent simian viruses, and the hypothesised association between bovine leukaemia virus (BLV) and human breast cancer. To provide a broader comparative perspective, the discussion also includes examples of viruses with a lower economic impact, illustrating that zoonotic and oncogenic potential is not limited to commercially significant species. Biological barriers—including receptor specificity and immune defences—generally limit transmission; however, frequent human–animal interactions, consumption of contaminated food, and viral mutations may increase zoonotic risk. Advances in molecular diagnostics, such as polymerase chain reaction (PCR), next-generation sequencing (NGS), and serological testing, play a critical role in identifying emerging threats. Prevention strategies, including veterinary vaccination programs, biosafety protocols, and the One Health approach integrating human and veterinary medicine, are essential for mitigating risks. While current evidence indicates that oncogenic animal viruses do not significantly contribute to human cancers, ongoing surveillance and research remain crucial to detect emerging threats. Understanding viral oncogenesis in animals continues to provide valuable insights into cancer prevention and therapy in humans.