National Geographic News
 An ultrathin section of a Pithovirus particle.

A Pithovirus (above, as viewed by electron microscopy) was found to be still active and able to infect an amoeba.

Image courtesy Julia Bartoli and Chantal Abergel, IGS and CNRS-AMU

Stefan Sirucek

for National Geographic

Published March 3, 2014

Buried deep in the Siberian permafrost and untouched for over 30,000 years, researchers have discovered what is thought to be the newest representative of what are loosely known as "giant viruses."

A team led by Jean-Michel Claverie and Chantal Abergel of Aix-Marseille University in Marseille, France, made the discovery of the previously unknown virus, which has been dubbed Pithovirus sibericum and can be revived in the lab.

Their findings are detailed in a new article in the Proceedings of the National Academy of Sciences.

Lest Siberian excavation makes you think of frozen woolly mammoths, make no mistake: These giants are still decidedly microscopic. But in the diminutive world of viruses they're larger than normal specimens, measuring 1.5 microns in length and 0.5 microns in diameter. The pandoraviruses, the largest viruses previously discovered, also by the team of Claverie and Abergel, measure 1 micron in length and 0.5 in diameter.

"'Giant' viruses are loosely defined as the ones that you can see under a regular microscope," explained Claverie and Abergel when contacted via email.

Large and Complex

Giant viruses also dwarf other viruses in terms of genetic complexity. The newly discovered Pithovirus contains 500 genes, and the aforementioned Pandoravirus can contain up to 2,500.

For comparison, the HIV virus contains only about 12 genes, explained James Van Etten, a professor of plant pathology at the University of Nebraska, when reached for comment. (Van Etten is an authority on viruses and edited the new study.)

Amazingly, even after more than 30,000 years embedded in ancient permafrost, when Claverie and Abergel exposed amoebas in their lab to the virus, they found that the virus was still active and quickly infected the host cell. "We use amoeba on purpose as a safe bait for capturing viruses. We then immediately verify that they are not able to infect animal/human cells," stressed the researchers.

Giant viruses are not just bigger but are hardier than others as well, said the researchers. This hardiness, along with a favorable environment, likely helped the newly discovered specimen stay intact for the thousands of years that it did. Viruses are often destroyed or rendered inactive by a number of factors, including light and biochemical degradation.

"Among known viruses, the giant viruses tend to be very tough, almost impossible to break open," said Claverie and Abergel. "Special environments such as deep ocean sediments and permafrost are very good preservers of microbes [and viruses] because they are cold, anoxic [lacking oxygen], and in the dark."

Intricate and Varied

The past decade has seen something of a renaissance in the discovery of large, genetically complex viruses, with the discovery of three distinct groups (Mimivirus, Pandoravirus, and now Pithovirus) suggesting that viruses can be much more intricate and varied than previously thought, and that giant viruses may not be especially uncommon.

The newly discovered diversity in genetic makeup and morphology among viruses leads Van Etten to surmise that different types of viruses may have evolved separately.

"The idea that all viruses evolved from one common origin, I suspect is not true," said Van Etten.

Changing Climate: Growing Threat?

If long-buried viruses can be unearthed, what else might be capable of coming to the surface? Climate change as well as industrial activities may shake up the ancient ice enough to bring potential pathogens to the surface.

"Mining and drilling means ... digging through these ancient layers for the first time in millions of years. If 'viable' [viral particles] are still there, this is a good recipe for disaster," said Claverie and Abergel.

But Edward Mocarski, a professor of microbiology at Emory University, says the risk of a virus pathogenic to humans being released from the ice is very small.

"The idea would make a great movie but is extremely unlikely unless the virus came from a frozen human being who possibly died from a virus that is no longer in circulation," said Mocarski when contacted via email.

"A very small proportion [of the viruses on Earth] represent viruses that can infect mammals and an even smaller proportion pose any risk to humans."

University of Nebraska's Van Etten agreed that such a situation was unlikely but possible with the right conditions.

"The biggest source of genes on the planet is probably from viruses, and they're just everywhere, but in general they're highly specific for the organisms that they grow in," said Van Etten.

The researchers behind the discovery, Claverie and Abergel, believe that whether or not it's likely, such a scenario remains feasible. They counsel vigilance and continued testing. As their latest research has shown, large DNA viruses may remain infectious for very long stretches of time.

"The fact that we might catch a viral infection from a long-extinct Neanderthal individual is a good demonstration that the notion that a virus could be 'eradicated' from the planet is plain wrong and gives us a false sense of security. At least a stock of vaccine should be kept, just in case," said Claverie and Abergel.

Their research will now turn to assessing how real a threat these ancient viruses pose.

"We are now doing more work to analyze the DNA content of these permafrost layers in a search for the genetic signature of viruses resembling human pathogens," said Claverie and Abergel, who stressed that they are not attempting to "revive" any such pathogenic viruses, but rather hoping to determine the potential danger.

"If we find some [human pathogens], then the risk will become more real. If not, we will be safe."

Follow Stefan Sirucek on Twitter.

55 comments
Nikita Nikitos
Nikita Nikitos

Hi I want to know your opinion 

possible to consider this potentially dangerous virus 

compared with the new known



Hanna Loyolla
Hanna Loyolla

What if one of these "potentially dangerous" viruses is the new variola virus ?

Emily Grim
Emily Grim

What if one of these "potentially dangerous" viruses is actually a cure for cancer? 

Carz Minghetti
Carz Minghetti

"Giant' viruses are l defined as the ones that you can see under a regular microscope" 

Sherrie Buck
Sherrie Buck

Giant animals, giant viruses and yet not giant humans? There WERE giant humans..until the 1950s, in fact, giant human skeletons were reported throughout the USA on a massive scale in many local newspapers.

Aberame selvam
Aberame selvam

what are all the genes that made it to be pithovirus...???....very protective capsid.....made it to survive 30,000 yrs.....


Rosy M.
Rosy M.

We're probable not prepared for such an old Virus!

s. an
s. an

Then we all go back to the original world

Melissa Daniels
Melissa Daniels

Probing into unknowns with ancient viruses is kind of like poking a hungry bear with a stick! 

Jakob Stagg
Jakob Stagg

What could possibly go wrong? I hate to think about it.

Amara S.
Amara S.

It's like the script from the first ten minutes of a horror movie. We could call it, "Just Beneath the Surface."

Richmond Acosta
Richmond Acosta

Why did they assign a scientific name to this virus? Aren't virus non living things?

Victoria C.
Victoria C.

I wonder if this is a reason there's mass extinction back in the previous eras... 

and it infects the animals back then and not animals in present.

Fatema Zahra Rashid
Fatema Zahra Rashid

Does the ability of the 30,000 year old virus to infect  amoeba point to the fact that the organism has shown minimal evolution through the ages?

Doug Noble
Doug Noble

As good a way to go as any.


We know the nuclear option is inevitable.


I'd rather get a virus and become a zombie or something

Daniel Rolan
Daniel Rolan

This is a very similar warning/discovery as mentioned in the book "Life in the Universe" by Marshall Vian Summers, which describes the biological threat that planet Earth would pose to any Alien visitor to our world, making visitation or colonization extremely risky if not impossible for these visitors, unless of course Alien visitors used a proxy human leadership for the purpose of governance without needing to be physically present. The risk of bacteria and viruses posed by our biologically rich planet to space dwellers adapted to the sterility of space is really something to consider.

robert john
robert john

look at this virus but do not let it get in the wrong hands

Darren Glazer
Darren Glazer

Why can researchers NOT LEAVE WELL ENOUGH ALONE!!!!!!????? The viruses are genetically complex and our immune systems have no prior knowledge of them... Why revive them, in ANY setting?????

Rajko Udovicic
Rajko Udovicic

Find a remedy for it and destroy the virus before some idiot ables it to re-enact, as Selena Dodsworth said, approximately 45456161615 movies that end with the annihilation of the human race. (Plague Inc. anyone? :P)

Selena Dodsworth
Selena Dodsworth

There are approximately 45456161615 movies that explain why this was a bad idea

Michael Lopez
Michael Lopez

No. "Climate Change" (what a stupid phrase) won't hurt us. digging up dead viruses and reviving them will probably hurt us. I also find it funny that they claim to not be "reviving" the organisms, yet in the first paragraph it says this:



A team led by Jean-Michel Claverie and Chantal Abergel of Aix-Marseille University in Marseille, France, made the discovery of the previously unknown virus, which has been dubbed Pithovirus sibericum and can be revived in the lab.



Which tells me that they've done it. 

Paul Davies
Paul Davies

seams like a good way to start a pandemic

Diana Pham
Diana Pham

My first response is to ignore it till it goes away or kill it with fire, but I realize neither of those are viable options.

David Drozdowski
David Drozdowski

Yeah, I'm just wondering how they arrived at 30000 years, as opposed to 3000000, 300000, 3000, or 300 years... And don't say carbon dating in the Siberian permafrost... Maybe it was ice layers, haha.

ZEINEB MESSAOUDI
ZEINEB MESSAOUDI

une expression chez nous dit : à trop creuser on tombe forcément sur le " déchet humain", et là on voit à quel point c'est vrai , le déchet c'est l'énorme virus qui peut comme on le sait en cacher un autre.et dire que c'est peu probable qu'on trouve un virus dangereux pour l'homme est surement de l'inconscience ou mensonge   

Eric Sorensen
Eric Sorensen

As much as I support science, it is important to remember that scientists are not immune from hubris, especially when they tell us "there is nothing to worry about."

As we continue to dig deeper into the planet, we may end up with more than we bargained for...

KENNETH LANE
KENNETH LANE

Let's play with this and see what happens-----------

Michael Lopez
Michael Lopez

@Richmond Acosta  There is debate on that. It's organic.....it replicates (kind of)..... so it's half alive. lol. That's part of my issue with digging these up. I don't know if there is any real way of knowing if they are "dead". 

Rachael Z
Rachael Z

@Fatema Zahra Rashid  you seem to not understand evolution. No evolution would have occurred at all because evolution does not occur at an individual level. 

Fatema Zahra Rashid
Fatema Zahra Rashid

@Darren Glazer  Its funny how scientists have to prod at anything that has the minutest evidence of life... In response to your concerns though... I don't think that the revival of the virus would harm or pose a risk human health... It has been frozen under Siberian ice for 30,000 years... around the time that humans began migrating out of Africa where they had lived for over 70,000 years... The virus has not evolved to use humans as hosts...

Daniel Malanga
Daniel Malanga

@Darren Glazer  Because learning about new viruses not only tells us more about the ones we already know, but it gives us a head start in case a virus similar to this one does in fact infect humans. If we were to simply leave things alone humans would still be in the dark ages and dying from bubonic plague. 

Stefan S.
Stefan S.

@Michael Lopez  Hi Michael. Author here. The reasoning is that whatever is buried in the permafrost will be exposed eventually anyway when the ice melts and as humans mine and drill in the area, so the idea is to take preemptive action by studying what the ice holds so that we can be prepared.


As for your second point, the final paragraph is referring to pathogenic viruses  specifically (i.e. viruses that are capable of infecting humans). The scientists stressed that they always isolate any viruses and make sure they're not a type that's capable of infecting humans. The virus in question in this article only affects aboembas and is being kept in isolation. I hope that answers some of your questions.

Stefan S.
Stefan S.

@David Drozdowski  Author here. Yep it was carbon-dated from a sample taken from roughly 30 meters below the surface.

Brian Hughes
Brian Hughes

@David Drozdowski  Dating ice is actually pretty easy. Each year when snow settles it compacts the previous years snow into ice under it's weight. It is from counting these distinct layers of ice that we can determine the date from which they got the samples. Pretty much like counting the rings on a tree to determine the age.

Timothy Barnes
Timothy Barnes

@Rachael Z @Fatema Zahra Rashid  I believe you may be missing her point, which is that the newly-discovered virus is more "primitive" [i.e. large, 500 genes] than present HIV-type viruses, and she wonders if these particular archaic qualities negatively affect amoeba-infecting capability. I hope I interpreted her question correctly. If I did not, the relevance of size and complexity to ability to infect the amoeba is still intriguing.

Michael Lopez
Michael Lopez

@Rachael Z @Fatema Zahra Rashid  It does to some degree. I think the real point is that the amoeba is a basic cell, this virus can infect a basic cell. Where it goes from there should give us pause for concern given the nature of viruses to take on host DNA. 

Michael Lopez
Michael Lopez

@Fatema Zahra Rashid @Darren Glazer  It has not yet, but because viruses mutate (sometimes insanely fast) I wouldn't discount the idea that they can evolve to infect humans. Small chance, especially in a lab, but that potential is still there. 

Michael Lopez
Michael Lopez

@Stefan S. Hi author, I understand the reasoning, and while it makes some degree of sense in terms of drilling, it doesn't make as much sense in terms of "Climate Change". You mentioned in another response the core sample was from 30 meters. If that much Ice/permafrost melts in the next few hundred years I would be surprised. 

The "revival" issue appears in your FIRST paragraph. Where you chose the wording "Can be revived in the lab". I understand they are taking every precaution they can to make sure that these are incompatible with humans, but these things are 30,000 years old, so in my mind, reviving any of them could prove to be a bad idea. 

I would assume further research would include exposing these viruses to tissue that it can infect. Without knowing how quickly these viruses can mutate (or what can "kill" them) we may be opening pandora's box so to speak.

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