As if the flu weren't terrifying enough, French researchers have discovered the largest viruses to date. A pair of giant viruses discovered in underwater sediment samples measure 1,000 times bigger than the common flu virus by volume.
The study, published Thursday in Science, reveals two giant viruses found off Chile's central coast and a freshwater pond near Melbourne. These massive viruses did not contain "morphological or genomic resemblance to any previously defined virus families," the scientists wrote. They are part of a proposed pandoravirus genus and don't pose a serious risk to humans, according to the researchers.
"The amphora shape of the Pandoraviruses and their unique genomic content made us associate them to the Pandora box," the scientists told Fast Company in a statement. "The opening of the box will definitively break the foundations of what we thought viruses were."
When the scientists first encountered a giant virus in 2003, they thought it was a bacteria but found no such DNA to back up that hypothesis. With more than 2,500 genes, the two hulking viruses are vastly more complex than the flu virus, which has 13 genes.
Jean-Michel Claverie, who coauthored the paper, told NPR the pandoviruses could have "emerged from a new ancestral cellular type that no longer exists"—possibly from Mars, he added.
So how rare are these pandoraviruses?
"The fact that two of them were found almost simultaneously from very distant locations either indicate that we were incredibly lucky, or that they are not rare," the scientists said. "One explanation for their late discovery would be that they are only found in sediments, an environment that has not been well explored, and that is also difficult to work with. As far as we know, this is the first recovery of viruses from sediments."
[Image: Chantal Abergel and Jean-Michel Claverie]