'Zombie Viruses' Hidden in Ice: Are They Dangerous? What the Expert Says

Viruses and other pathogens hibernate for centuries, even thousands of years. Preserved in the oldest layer of glaciers, the so-called permafrost: a sort of fairytale "enchanted castle," where the absence of oxygen and light can prolong certain life forms for incredible lengths of time. A "cold bank" that has trapped traces of the past in time, including microorganisms that are anything but welcome to humans. In short, a frozen world that climate change, with rising temperatures increasingly thinning the permafrost, could bring to light. And we can't be sure that these invisible enemies will resurface "defused." Quite the opposite. Researchers have even coined the term "zombie viruses" for ancient Highlander pathogens that remain infectious once they emerge from hibernation. This isn't just a hypothesis.  

Although this area of ​​research currently remains a small niche, some studies have demonstrated its potential. A French study conducted a few years ago (by the Universities of Marseille and Aix-en-Provence) isolated prehistoric megaviruses from Siberian permafrost. These viruses were found to be capable of infecting unicellular organisms such as amoebas, but not more complex life forms. In 2016, again in Siberia, an incident outside laboratories, caused by a particularly severe heatwave, confirmed the survival capabilities of certain microorganisms: the thawing carcass of a reindeer that had died decades earlier released anthrax spores, with tragic consequences for the local population, culminating in the death of a child.  

The research on pathogens in the ice, epidemiologist Gianni Rezza, associate professor of Hygiene at the Vita-Salute San Raffaele University of Milan, tells Adnkronos Salute. Milano, “gained momentum when studying the Spanish flu. The frozen bodies of people who died from the virus were studied, isolating the preserved pathogen from the ice. Obviously, this doesn't mean the virus remains viable or intact. In the case of the Spanish flu, DNA and RNA sequences were found. Even in the case of the French group that discovered megaviruses in Siberia, the pathogens were found to be capable of infecting only amoebas, not humans. From a scientific standpoint, however, we can't completely rule out that a hibernating virus could somehow become viable again, replicate, and infect animals or even humans. It's a possibility. How likely this is, given the current state of knowledge, no one knows.”  

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Obviously, the expert continues, "if a virus already circulating, like measles, were to resurface, not much would change." So what should we be afraid of? "Viruses or bacteria that have circulated in the past, no longer circulating now, and against which we have no tools. Ironically, if a smallpox zombie virus, now eradicated, were to reemerge, we would still be able to defend ourselves because we have vaccines available." More fearsome, however, are "aggressive microorganisms responsible for past epidemics, against which the human body is ill-equipped and medicine has no answers." In short, a future pandemic could come from the cold, not just from classic reservoirs like birds and wild animals. "It's obviously not an alarm," Rezza clarifies. "We can't say: if the permafrost melts, then humanity is in danger. That would be unreasonable and irresponsible. It's a hypothesis worth studying, but it's not far-fetched."  

At the moment, however, research on the topic "isn't extensive," the epidemiologist reports. "There are niche studies. The issue has been the subject of specific research by a few groups, and more out of curiosity than systematic work." Now, however, "having established that climate change is an absolute fact—even if its human impact is the focus of ongoing discussion—a reflection on the need to delve deeper into these issues is needed. This year, the freezing level in Italy has exceeded 4.000 meters. Without wishing to create widespread alarm or boast certainties, if global warming is having such an effect in some areas as to erode the permafrost, it's clear that the issue deserves more attention. The little research that has been conducted so far has been pioneering; it's time to consider more systematic projects, both by researchers and by the institutions that fund the research."  

(Adnkronos)