Unpredictable weather raises ‘zombie’ diseases from the ground
The death of a boy and his grandmother this month in the far north of Russia after an anthrax outbreak raises questions about the impact of climate change on other pathogens that have been suspended in the ice.
Melting ice caps, rising sea levels, unpredictable weather patterns leading to widespread flooding and, conversely, drought – the known consequences of global warming are bad enough.
But to that catalogue of disasters may be added – right out of the Hollywood scriptwriter’s playbook – the return of deadly “zombie” diseases, reawakened from slumber by the melting of ice that has entombed them for decades or centuries.
This month, an outbreak of anthrax in the far north of Russia claimed the lives of a 12-year-old boy and his grandmother, among 41 children and 31 adults struck down by a disease not seen in the region since 1941. Hundreds of reindeer are also reported to have died.
It is not yet clear where the anthrax came from, but scientists are examining two possibilities – that the dormant but still infectious spores were released from the remains of infected animals or humans buried more than 70 years ago and now being exposed as the region’s permafrost melts.
In either case, Alexei Kokorin, head of WWF Russia’s climate and energy programme, says back then “they didn’t bury deep because it’s hard to dig deep in permafrost”.
Now, however, that permafrost is on the retreat, raising concerns about what might lie beneath. Summer thawing in the region normally melts the ice to a depth of about 30 centimetres, but this year it has exceeded a metre, exposing shallow human and animal graves.
It is not the first time a long-dormant virus has risen from its slumbers. In a paper published a year ago, a team of French and Russian scientists revealed that since 2003 four viruses had been discovered in a single 30,000-year-old sample of permafrost.
According to a paper published in the journal Proceedings of the National Academy of Sciences of the United States in August last year, all four were capable of infection.
Luckily for us, the targets of these primitive, “giant” viruses – so large they can be detected with a normal microscope – are only certain types of amoebae.
But, the authors caution, “the fact that these viruses retain their infectivity in prehistorical permafrost layers should be of concern in a context of global warming”.
Other viruses poised to emerge from icy tombs might not be so benign.
Smallpox, caused by the variola virus, is believed to have first infected humans about 12,000 years ago. By the 18th century, it was killing half a million people a year in Europe alone and in the 20th century claimed the lives of as many as 500 million people worldwide.
It was the first disease to have been fought on a global scale and, in 1980, after an 18-year immunisation drive, the World Health Organisation declared that, apart from a few samples kept in secret and highly secure laboratories, it was eradicated.
Or maybe not. After the recent anthrax outbreak in Russia, scientists there told The Siberian Times they feared “born again” smallpox could rise from the graves of victims buried more than 120 years ago.
In the mid- to late 1800s several smallpox epidemics ravaged settlements north of the Arctic Circle, wiping out whole communities.
“There was a town where up to 40 per cent of the population died,” Boris Kershengolts, deputy director at a Siberian biological research institute, told the paper. “Naturally, the bodies were buried under the upper layer of permafrost soil, on the bank of the Kolyma River.”
Now, more than a century later, he says, “Kolyma’s floodwaters have started eroding the banks”, exposing the graves.
Scientists from the virology and biotechnology centre in Novosibirsk examined corpses, partially preserved by the ice, and found signs of smallpox infection and telltale fragments of the virus’s DNA – not enough to infect, but a possible harbinger of worse to come.
The Yakuta region of Siberia appears to be full of surprises. In 2003, a Russian scientist hoping to find ice-preserved mammoth cells suitable for cloning excavated a pair of well-preserved legs. The required cells proved elusive. But Vladimir Repin and colleagues from the geocryology department at Moscow State University continued their work in the area known as Mammoth Mountain and were rewarded with an unexpected discovery – a strain of the bacteria bacillus cereus.
It was, they wrote in a paper published in the journal Genome in August 2013, “a long-term survivor of the extremely cold and close environment” and was believed to be “as ancient as the permafrost sample from which this strain was isolated”. Three million years old, in fact, and to the surprise of the scientists, still capable of being cultured in a lab.
“It seems astonishing that bacteria trapped in frozen soil can survive soil radiation and other damaging agents at temperatures of nearly minus 3°C and under the conditions of a closed environment and almost total deprivation of energy sources,” they wrote.
Modern strains of bacillus cereus are associated with food poisoning in humans, and can occasionally prove fatal. Quite what the so-called “F” strain found at Mammoth Mountain might be capable of remains uncertain, but it was “surprisingly” similar to modern strains of the bacteria.
Perhaps even more surprising was that Anatoli Brouchkov, one of the team, injected himself with the bacteria, believing its resilience and longevity meant it might hold the key to human immortality.
He claimed to feel healthier and stronger, but science may – or may not – have a long time to wait to see if he is right.
Ice is not the only medium that can offer refuge to dormant bacteria. In October 2000, scientists at Pennsylvania’s West Chester University reported the discovery of a “previously unrecognised spore-forming bacterium” that pre-dated the dinosaurs. More than 250 million years old, it was found trapped in a bubble of fluid inside a salt crystal 564 metres underground in the Guadalupe Mountains in west Texas.
“We all feel reasonably comfortable that this particular organism isn’t going to attack anything,” one of the scientists said at the time.
Some jurassic microbes could even do us good. In 1995, the prehistoric bacteria bacillus sphaericus, trapped in the stomach of a bee, which in turn had been entombed in amber, was revived by scientists at California Polytechnic State University after more than 25 million years. DNA analysis showed it was related to bacteria alive on the Earth today but it “appeared to be a harmless species”, they concluded.
The find offered a chance to study the evolution of bacterial species, wrote the authors of a paper published in Nature, “and may represent a brand-new source of pharmaceutical drugs and industrial enzymes”.
In fact, it is now used as an insecticide, to kill the larvae of the mosquito and other insects.
Nigel Brown, emeritus professor of molecular microbiology at the University of Edinburgh, says we should not be unduly worried about the prospect of microbial “comeback killers” returning from the grave.
Finding anthrax in the permafrost was “feasible and not surprising”, he says. “Yes, it is slightly scary, but then there are lots of scary things in science. Due precaution has to be the rule in such circumstances.”
Anthrax, Prof Brown says, does not need a deep freeze to survive. “It forms a very resistant spore, and it’s the spore that survives for a long time and causes the infection.”
For proof of the ability of anthrax to survive in normal temperatures, he says, we need look no farther than the small Scottish island of Gruinard, quarantined for half a century after British scientists seeking to develop biological weapons tested the killing power of weaponised anthrax on a flock of sheep in 1942.
One of the sobering conclusions of the experiment, which left the island dangerously contaminated until its topsoil was removed and the ground sprayed with formaldehyde in 1986, was that 100 kilograms of anthrax spores unleashed on a city would kill 3 million people.
Not all bacteria are as resilient as bacillus anthracis, which explains why archaeologists excavating the sites of mass burials in London before railway projects start are not toppling over after exposing the bodies of victims of the bubonic plague.
Bubonic plague killed 15 per cent of London’s population in a single year in the 17th century. Most were thrown into communal burial pits, 36 of which were identified and mapped in 2014 by Historic UK. Several lie under what are now public squares in the heart of the city.
Opening them up is safe, says Prof Brown, “for two reasons, relevant to many diseases, not just Bubonic plague. One is that relatively few infectious organisms go through this spore stage, which the anthrax bacillus does, so they’re not highly resistant to temperatures and chemicals in the environment”.
Bacteria such as Yersinia pestis, which causes the plague, “are much more sensitive. Also, they require fairly rapid passage from host to host in order to survive”.
As Earth’s changing environment threatens to expose more micro-organisms from the past, it would, he says, be a useful if time-consuming exercise for science to draw up a list of the most resilient organisms, and thus most potentially dangerous.
In the meantime, should we be running around and panicking about the prospect of a historic pandemic rearing its ugly head once again?
“No more than we should be running around and panicking about other aspects of global warming,” Prof Brown says, which sounds suspiciously like science-speak for “Yes”.
“There are a large number of, shall we say, unintended consequences of global warming and this is one of them.”
And, living in the beautiful but low-lying English county of Wiltshire, which over the past few years has been increasingly prone to flooding, he has other more immediate concerns linked to climate change. “I won’t be fleeing for the hills,” he says, “unless we get any more flooding this year”.
Or, as a Bloomberg report put it, for now, “anthrax-spewing zombie deer are the least of your warming planet worries”.