Bacteria and viruses can remain trapped in ice and permafrost—a layer of frozen soil—for up to a million years.
But as Earth’s climate warms, they are coming to life.
Permafrost is an ideal environment for bacteria to hide for long periods of time as a result of its lack of oxygen and darkness. Typically, permafrost up to about 20 inches deep will melt during the warmer seasons, but climate change is causing deeper layers to thaw.
While we’ve always co-existed with bacteria and viruses, these traditionally frozen surfaces on earth could expose us to pathogens we’ve never encountered before, and our immune systems likely wouldn’t know how to respond to them.
It’s hard to say what would happen if we were exposed to bacteria that haven’t been around for thousands of years, but—this could be about to happen.
How Bacteria Trapped in Ice Reactivate—a Curious Case of Reindeer and Anthrax
Three years ago this month, in the Yamal Peninsula in the Arctic Circle, a 12-year-old boy died and more than two dozen people were hospitalized after being infected with anthrax, a bacterial disease affecting the skin and lungs of sheep and cattle, but one that can be transmitted to humans .
How did this happen?
Experts speculate that a reindeer infected with anthrax died and its carcass remained in permafrost, but in the heatwave of summer 2016, the permafrost thawed . The infected carcass then had an opportunity to further decompose and release anthrax into the water, soil, and ultimately, the food supply of thousands of nearby reindeer, which then led to human infection.
The Arctic Circle, where the suspected anthrax-infected reindeer died, is currently experiencing rising temperatures three times faster than the rest of the globe. And this isn’t the only reindeer that died from anthrax—more than a million reindeer died as the result of anthrax in the early 1900s, and most of these corpses are buried superficially across thousands of different locations in Russia .
But Anthrax Isn’t the Only Disease, and Scientists Have Proven Just How Easily Bacteria in Ice Can Be Revived
Permafrost doesn’t just hold anthrax-infected reindeer—other people and animals are buried there, too, including those that died from the Spanish flu virus, smallpox, and the bubonic plague .
These diseases that aren’t an issue in our modern world—the last-known case of smallpox was in 1977 and Spanish influenza hasn’t been seen since 1919 .
But people who died of these illnesses are buried in layers of soil that, typically, remain permanently frozen. But now, research shows that deadly viruses may make a reappearance, especially near where victims were buried .
Bacteria frozen in ice can be brought back to life, affecting nearby water supplies as we’ve seen in the case of the infected reindeer. Apparently, some bacteria are entirely unaffected by centuries of inactivity in a frozen environment. For example, scientists at NASA revived bacteria frozen for over 30,000 years in a pond in Alaska. Once they melted the ice and incubated the bacteria, they became mobile, apparently not affected by the long freeze .
Scientists also brought an 8-million-year-old bacterium back to life that was trapped in a glacier in Antarctica but noted that the microbes’ viability was “seriously compromised” . In other research, scientists brought back two viruses that had been lying dormant in permafrost for 30,000 years .
Once these two viruses were revived, they became infectious. However, these particular viruses only affect single-cell organisms, but scientists believe that other viruses that can infect humans can be revived in the same way.
Fortunately, not all bacteria are capable of being brought back to life after being frozen. Anthrax can because the bacteria forms spores, which are very resilient and can survive frozen for more than 100 years. Other spore-forming bacteria—including fungi as well—can also survive in permafrost.
Do Bacteria Trapped in Caves and Mines Pose a Risk?
We’ve talked a lot about permafrost and ice in regards to dormant viruses and bacteria—but what about those that lie deeper in the earth?
Just two years ago, scientists from NASA claimed they found bacteria that were anywhere from 10,000 to 50,000 years old inside crystals in a mine in northern Mexico. Once removed from the crystals, these bacteria came to life and began multiplying. The scientists say these microbes are unique and may be a new species, but the results have not yet been published .
This is just another example of how bacteria we’ve never been in contact with before can easily be brought to life—and potentially affect our species.
In New Mexico, even older—and more resistant—bacteria was found in the Lechuguilla Cave, which lies 1,000 feet underground. These bacteria haven’t been exposed to the surface in millions of years. Despite its isolation, these bacteria have become resistant to 18 types of antibiotics, including those considered as “last resorts”.
The bacteria were found to be resistant to 70 percent of antibiotics, able to render many of them ineffective . Antibiotic resistance is a real problem, arguably one of the largest current challenges to public health today .
Fortunately, this bacteria doesn’t harm people but may have naturally evolved to resist antibiotics, suggesting that antibiotic resistance has been around for quite some time, perhaps as a way for organisms to avoid being killed by other organisms.
Should We Be Worried?
We can’t know the exact risk, but we do know that as the Earth gets warmer, layers of permafrost and ice will melt, and what they might expose is anyone’s guess. In addition, northern countries will become more vulnerable to diseases traditionally present in much warmer climates, such as malaria and dengue fever.
The Centers for Disease Control and Prevention (CDC) says the probability of the Spanish influenza virus “re-emerging from a natural source appears to be remote” . But bacteria that can revive and infect us are absolutely a possibility, and our immune systems would not be prepared because they would have never encountered these agents before—how worried we should be isn’t clear, but we suspect time will tell.
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