A giant, stealthy virus astonishes researchers

Researchers from Tokyo University of Science (TUS) have discovered a new type of giant virus, named “Furtivovirus,” in samples taken from the Inasegawa River in the city of Kamakura, Japan.

The virus takes its name from the Latin word furtivus, meaning “hidden” or “stealthy,” in reference to the difficulty of identifying and isolating it during the initial analysis of the sample.

This discovery comes as part of a series of recent findings involving other giant viruses, including “Ushikuvirus,” which some of the same researchers discovered earlier this year.

Giant viruses are known for possessing large and complex genomes compared with conventional viruses, and for exhibiting unusual biological capabilities that make them resemble complex living organisms in some respects, despite remaining outside the traditional classification of the “tree of life.”

Although all viruses depend on infecting living cells in order to reproduce, this type of virus shows remarkable diversity in the ways it interacts with host cells.

Researcher Masaharu Takemura of Tokyo University of Science said that these viruses “belong to the same group, but use the cell nucleus in different ways,” adding that understanding these mechanisms could reveal new dimensions about the nature of viruses and their role in the biological system.

“Furtivovirus” stands out for characteristics that make it an exceptional case among giant viruses, as genetic analysis showed that it occupies an intermediate position between two different groups of these viruses, which differ clearly in the size of their genomes.

Based on this, the researchers propose classifying the virus within a new family they have named “Manesviridae,” which is believed may include other giant viruses with similar characteristics.

This virus also differs in the way it reproduces inside the cell. While some giant viruses keep the cell nucleus intact in order to reproduce within it, and others destroy the nuclear membrane and reproduce outside it, “Furtivovirus” adopts an intermediate strategy: it dismantles the cell nucleus after infection, then exploits its contents to reproduce within the nucleoplasm.

The researchers describe this mechanism as unprecedented among giant viruses known so far. They believe that studying this type of virus could help provide a deeper understanding of how viruses have evolved over time, how they adapt to different environments, and how their genomes change.