[Ed. – Because global warming.]
The virus is classified as a “giant” virus because it’s visible by light microscopy. Mollivirus sibericum carries a complex genetic structure that houses more than 500 genes, according to the study’s abstract. The influenza virus, in comparison, has only 8 genes.
The same team that discovered Mollivirus sibericum found another 30,000-year-old virus, Pithovirus sibericum, in the same Russian permafrost. As described in PNAS last year, those scientists revived a sample of Pithovirus sibericum in safe lab conditions and determined it was still infectious, though it only affects amoebas.
These cases raise concerns about such viruses in the context of melting permafrost.
“The fact that two different viruses retain their infectivity in prehistorical permafrost layers should be of concern in a context of global warming,” the PNAS study’s abstract says. “Giant viruses’ diversity remains to be fully explored.”