31 Gastric cancer ranks fifth in global cancer incidence and causes over 650,000 deaths each year. Clinical management has long been limited by a lack of effective early screening tools, with most patients diagnosed at advanced stages when treatment options are severely restricted. A new study has systematically profiled the virome in blood and faecal samples from gastric cancer patients, providing a detailed picture of the disease’s virological landscape. The research, published in Virologica Sinica, provides the first comprehensive atlas of blood and gut virome changes in gastric cancer. “In healthy individuals the blood virome is dominated by bacteriophages, viruses that infect bacteria,” explains Dr Wang Li, corresponding author of the study. “But in gastric cancer patients, over 80% of viral sequences belong to a single family, Anelloviridae, viruses that infect humans but rarely cause disease. At the same time, viral diversity plummets, as if an entire ecosystem is being taken over by one species.” The researchers identified 67 provisional novel anellovirus species and one entirely new virus, a gemykibivirus, in the blood of gastric cancer patients. This discovery substantially expands knowledge of the hidden diversity within the human blood virome. Anelloviruses are known to infect humans widely, yet are rarely linked to disease in healthy people. Their marked expansion in the blood of gastric cancer patients, alongside a sharp drop in overall viral diversity, points to a profound remodelling of the circulating viral community. “Interestingly, the gut told a different story,” says Li. “While blood diversity declined, the gut virome of cancer patients showed increased diversity, with a mix of bacteriophages. Different body compartments respond to cancer in distinct ways.” “This indicates that the virome is not a single entity but is compartment-specific, with each site following its own ecological rules,” says co-corresponding author Dr Shaokun Pan. This compartment-specific view challenges earlier assumptions that the human virome behaves as a uniform system. The most clinically relevant finding emerged from LEfSe analysis, which identified Betatorquevirus, a genus within Anelloviridae, as a key viral signature distinguishing gastric cancer patients from healthy individuals. Network analyses further showed that anelloviruses negatively correlate with multiple bacteriophage families, suggesting they may outcompete other viruses in the bloodstream. “The expansion of blood anelloviruses holds promise as a non-invasive biomarker for gastric cancer,” adds Li. “Whether this virus can serve as a non-invasive biomarker requires larger prospective studies to validate its clinical utility.” Gastric cancer remains a major global health challenge, particularly because symptoms often appear late, and current screening methods are limited, with many cases detected only after the disease has progressed. Non-invasive markers detectable in blood could transform early detection strategies. The identification of Betatorquevirus as a distinguishing feature, along with the broader dominance of Anelloviridae, raises the possibility that simple blood tests measuring these viral signatures might one day help identify patients at risk or those already developing the disease. Larger prospective studies are needed to confirm whether the observed anellovirus expansion reliably predicts gastric cancer across diverse populations and disease stages. Researchers must also clarify the biological mechanisms behind the compartment-specific changes and determine whether the viral shifts contribute to cancer development or simply reflect the altered immune and physiological environment created by the tumour. All data from the research have been made publicly available, a move expected to accelerate independent analyses and collaborative efforts worldwide. Scientists can now examine the sequences in greater detail, explore associations with clinical outcomes, and test potential diagnostic applications. While the findings are promising, they remain preliminary, and validation in larger and more varied patient cohorts will be required before any clinical use can be considered.