A report made to the National Academy of Sciences of the United States of America this past November, and just published in their Proceedings a month ago reveals a “giant virus” (able to be seen under a standard microscope, unlike most viruses) has become active after being thawed from a sample of Siberian permafrost. Researchers at the Russian Academy of Sciences had sent Dr. Abergel and Dr. Claverie, two of the report’s authors, small pieces of permafrost extracted from a Siberian riverbank in 2000. This particular area of Siberia has been changing over the past few decades as its permafrost layer thins and the permafrost line in general retreats north.
The viruses average 1.5 micrometers long, the largest ever observed. Their oddly long, narrow shape inspired the scientists to call them pithoviruses — “pithos” referring to ancient Greek earthenware jars. The newly-discovered pithovirus contains 500 genes; another giant virus, the pandoravirus, can contain up to 2,500. For comparison, the HIV virus contains only about 12 genes. The sturdy protein shell of the pithoviruses are what allowed them to survive in stasis this long. A “lipid envelope” virus, such as influenza or AIDS, is more fragile and cannot survive being frozen as well.
Thankfully, the pithoviruses from Siberia have only been found to infect amoebas. Whether there are more of these ancient pathogens deeper in the threatened permafrost that could harm mammals or even humans in specific is a concern not just to the scientific team at Aix-Marseille University, but virologists in general. The likelihood of a human-hazardous virus found in the ground is fairly small, although the French scientists continue to search for the genetic signature of viruses resembling human pathogens. A virus revived from a frozen human or Neanderthal sample would be far more likely to be dangerous; but overall, the probability is still extremely small that we’ll be at hazard by this Hollywood-movie-like situation.