‘Zombie viruses’: Ancient diseases climate change will bring back

Science and Health

A number of zombie viruses have been pulled out from the permafrost by scientists, giving insight into what secrets may lie hidden beneath the ice.

Permafrost is an area of ground where everything, including a host of organic matter, has been perpetually frozen for millions of years. This cold terrain constitutes roughly a quarter of the Earth’s Northern hemisphere.

But worsening climate change has seen permafrost slowly begin to roll back, the thawing ice now giving way to everything it had kept hidden. 

This is problematic for a couple of reasons. The first is that much of this organic matter that is now exposed will decay and end up releasing carbon dioxide and methane, which are greenhouse gases, therefore making climate change even worse.

But the second reason is that it will also revive untold numbers of ancient prehistoric viruses forgotten by time, now ready to come back to the surface.

A Pandoravirus (Illustrative). (credit: Wikimedia Commons)

Right now, scientists have taken a look at some of these viruses they managed to extract from the permafrost themselves. So far, these viruses aren’t able to infect humans and have only been shown to infect single-cell amoebas. However, that isn’t to say there aren’t any dangerous diseases – in fact, we know life-threatening diseases lay in wait.

Here’s a list of four zombie viruses lying under the permafrost, and one other not-so-zombie virus that already has had, and will continue to have, lethal consequences. 

1: Pithoviruses

With a name deriving from the Greek term for large jars, these viruses are categorized as giant viruses and almost all known examples were found in the Siberian permafrost. 

In fact, it was the discovery of the first of these, Pithovirus sibericum, that kicked off the concerns of zombie viruses when it was first found in 2014 in a 30,000-year-old piece of Siberian permafrost. However, it wasn’t the first zombie virus to be found in the permafrost. Scientists had found some even as far back as 2003.

The virus itself is harmless to humans, so no one was ever actually concerned that it could threaten humans. But what did raise concerns is the fact that the virus samples were still viable. 

Another Pithovirus was discovered later, known as the Pithovirus mammoth. Like P. sibericum, P. mammoth is harmless to humans and only exists in amoebas. 

This virus was one of 13 zombie viruses that was revived from the Siberian permafrost fairly recently, with a study about it published back in late February 2023 in the peer-reviewed journal Viruses

This sample also had some petrified mammoth wool, which is where the P. mammoth virus was found.

Another subgroup of Pithovirus also deserves some note, the Cedratvirus. These are also giant viruses and are related to Pithoviruses and were found in different locations in the Russian Far East. 

However, the relationship is noted to be very distant.

2: Mollivirus sibericum

This virus was found alongside P. sibericum in the same sample and is also large enough to qualify as a giant virus. 

Less research has been done on this virus, but it has been confirmed to pose no risk to humans or animals.

3. Pandoraviruses

The term “giant virus” refers to a virus that is both large in size and in its genome count. In that regard, Pandoraviruses are absolutely enormous. 

These viruses are so huge that when they were first seen by scientists, they were overlooked because they were considered to be too big to actually be viruses. Rather, people thought they were bacteria.

The fact that they are so large has led some scientists to propose that this may indicate the existence of something entirely different, a new “domain” of microbes and therefore a new branch on the evolutionary tree, though this is not accepted by the wider scientific community.

In terms of gene count, they possess around 2,500 genes. Most modern viruses have, at most, 20 genes. For example, the virus that causes influenza has seven genes and HIV has just nine.

Even Pithoviruses have around just 460 genes. 

The most notable of these Pandoraviruses is Pandoravirus yedoma, which was found at the bottom of a lake. This virus is notable for being the oldest virus ever discovered, being around 48,500 years old.

However, Pandoraviruses have been known to science since 2013. Not much is known about them because they live in areas that aren’t always well-studied. As far as we know, though, they pose no danger to human life in any way.

The same is also true of the Pandoravirus mammoth, which was found in the same mammoth wool sample as the aformentioned Pithovirus.

It, too, seems to pose no threat to humans.

4. Megavirus

With a name like Megavirus, one might think that these viruses are very big. And they would be right – until the discovery of Pandoraviruses in 2013, they were the biggest known viruses with the most complex genome. 

Technically, this virus is part of the Mimivirus family, and the one Megavirus known to exist, Megavirus chilense, was found in 2010 near Chile.

But then, in that same mammoth wool sample in the Russian permafrost, scientists found another sample, Megavirus mammoth.

This one, too, only infects amoebas, so humans aren’t at risk.

5. Anthrax

All of these aformentioned zombie viruses can’t kill humans. What they represent – the inevitable revival of ancient viruses as the ice thaws – may be dangerous, but the viruses themselves are harmless.

But there is verified evidence of dangerous pathogens that lurk beneath the permafrost. They have killed before and they can kill again.

One such example happened in 2016, when thawing permafrost in Siberia affected dozens of people and over 2,000 reindeer, killing at least one child.

Anthrax isn’t technically a virus. Rather, it’s a disease caused by the bacteria Bacillus anthracis

This disease is extremely dangerous and while it is treatable, should the treatment happen in time, its potential deadliness is so great that countries have used it as a bioweapon.

This disease is spread out in different animals and is zoonotic, jumping from animals to people. 

But this bacteria is very hardy and can survive in extreme conditions, such as on the corpses of animals. And the ice can preserve it.

This is what happened in 2016. Anthrax was last spotted in this region of Siberia in 1941. However, an unusually warm summer due to climate change – temperatures were as high as 35 degrees Celsius – caused the permafrost to thaw, uncovering animal burial grounds and remains, which could have polluted the groundwater, The Guardian reported at the time.

And this is far from an isolated instance. Anthrax can be found everywhere in the world, even in Antarctica. And other dangerous diseases could be lying in wait too, with global warming making their resurgence and potentially fatal consequences not a matter of if, but when.

Jerusalem Post Staff contributed to this report.