What is it about?
Viruses sometimes leave permanent traces of themselves in the DNA of the animals they infect. These “fossil viruses,” called endogenous viral elements (EVEs), can be used to track the natural hosts of viruses over evolutionary time. In this study, we scanned hundreds of animal genomes and uncovered many such viral fossils belonging to the circovirus family. By comparing them with modern circoviruses, we discovered that cycloviruses - a poorly understood branch of this family - are strongly associated with insects and other arthropods. This is the first solid evidence of their host range, and it suggests that reports of cycloviruses in humans most likely reflect contamination from insect material rather than genuine human infection.
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Why is it important?
In 2013, researchers reported a new cyclovirus (CyCV-VN) in patients with brain infections in Vietnam, raising alarm that it might be a novel human pathogen. Similar claims soon followed for other human-associated cycloviruses. But the evidence was circumstantial: the virus was detected, not proven to cause disease. Our study provides an evolutionary cross-check. By showing that cycloviruses are firmly rooted in insect lineages, we demonstrate that their appearance in human samples is more plausibly explained by environmental contamination (for example, from mites or other arthropods) rather than true infection. This finding directly challenges claims of human disease causation and shows that EVEs can be a critical tool for clarifying host associations in virus discovery. More broadly, it highlights how viral fossils can help distinguish between real zoonotic threats and misleading noise.
Perspectives
For me, the most exciting part of this work was showing that endogenous viral “fossils” can be used as a practical tool for modern virology. EVEs reveal the deep past of viruses while also helping us interpret today’s flood of sequence data. I hope this paper encourages others to treat EVEs as more than evolutionary curiosities — they can serve as a cross-check on metagenomic virus discovery, helping to avoid false claims and focus attention on genuine host–virus relationships.
Dr Robert Gifford
Stellenbosch University
Read the Original
This page is a summary of: Insights into Circovirus Host Range from the Genomic Fossil Record, Journal of Virology, June 2018, ASM Journals,
DOI: 10.1128/jvi.00145-18.
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