After 30,000 years in Siberian permafrost, the biggest virus ever identified is still deadly.
This virus attacks amoebas, not people. Scientists who found the huge virus warn that melting, drilling, and mining old permafrost might release viruses that infect humans.
The 1.5-micrometer Pithovirus sibericum particle is 25 to 50% longer than previous record holders and 15 times longer than HIV. P. sibericum, shaped like another big virus, has a small genome, its discoverers write March 3 in the Proceedings of the National Academy of Sciences.
Evolutionary scientist Eugene Koonin of the National Centre for Biotechnology Information in Bethesda, Md., who was not involved in the study, says “It’s quite different from the giant viruses already known.”
French researchers Jean-Michel Claverie and Chantal Abergel of Aix-Marseille University headed the team, which discovered the first gigantic virus 10 years earlier. Researchers used a light microscope to observe Mimivirus, a huge bacterium. Before the discovery, Claverie recalls, “we had this silly idea that all viruses were basically very small.”
Years later, the discovery of many Mimivirus-like viruses prompted researchers to think that all large viruses belong to a single family. Claverie, Abergel, and collaborators found a second, bigger family of Pandoraviruses in the sediment of a Chilean river and an Australian pond last summer.
The group discovered another big viral family this week, shaking the pitch again.
“Now, with this Pithovirus, we are totally lost,” Claverie continues. “Adds to confusion.”
The team investigates unexplored locations for novel viruses. Claverie, Abergel, and colleagues searched Siberia’s frozen soil after reading about a plant recovered from 32,000-year-old permafrost (SN: 4/7/12, p. 15).
Permafrost samples were put to amoebas dishes and observed for death. They did. The researchers found several oval-shaped virus particles in the dead amoebas under a microscope.
Koonin said scientists don’t know how huge enormous viruses can become. “I’d be excited but not surprised if something bigger comes up tomorrow.”
However, he is not concerned about permafrost viruses infecting people.
“This is a ridiculous idea.” He claims long-frozen soil does not conceal more uncommon viruses than other conditions.
Abergel admits amoeba-infecting viruses are simpler to detect than human-infecting ones.
Because Pithovirus has lasted so long, Claverie thinks it’s easy to assume other deadly viruses may too.
Koonin is more concerned in large viral implications of the latest discovery. He claims scientists have barely started to exploit their variety.
Claverie says, “Either we are very good, we are very lucky or there are many of them.”
