The first time I read of zombie viruses being released from melting permafrost in our warming environment, my antennae wiggled. I suspected this might be more social media junk science that flows so endlessly on the web. But I did see a couple of credible articles suggesting this was hypothetically possible (one in The Atlantic comes to mind), so I lowered my skepticism shield long enough to investigate further.
It’s an issue worth exploring. There is so much frozen plant and animal life going far back in time that a reservoir of pathogens possibly being released into our environment with the ongoing thawing might pose a significant threat to human and animal health.
“Might” is one way of looking at this issue but, for most pathogens, “not likely” would be a better narrowing of probabilities.
Veteran microbiologist Mike Hays explained the basic picture to geneticist and sci-fi author Dan Kolboldt, starting with viruses.
Viruses can be the scariest, both for virologists and for laypeople. Some can replicate with amazing efficiency, and some are horribly contagious. However, Hays says a zombie virus would have to be a “high velocity transmission virus.” In real time, these have the capacity to infect cells and hijack some cellular processes. But Hays says there is no evidence they have the genomic ability to cross over into a zombie state and survive ready to launch new infections in the future.
In a separate investigation, National Public Radio reporter Michaeleen Doucleff spoke with University of Pennsylvania paleopathologist Dr. Michael Zimmerman about zombie viruses.
He recounted how a graduate student went to a mass grave outside Nome, Alaska, and dug up frozen corpses of people who had died in the terrible 1918 flu pandemic. He was able to find and isolate the virus from pieces of the victims’ lungs, but was unable to grow any of the viruses anew in the lab. He could not bring them back to life.
And, Russian researchers isolated some frozen smallpox-infected tissue and could not grow any new smallpox viruses. So far, there is no evidence long-frozen viruses can come back from zombie state to life.
What about bacteria? That’s where “might” rather than “not likely” is a better descriptor.
For one thing, hibernating anthrax have infected livestock for millennia, coming back to life when conditions are right.
But in the case of anthrax, permafrost is not the growing medium, though transformation from hibernation to living pathogen is demonstrated. However, anthrax from non-frozen soil is markedly different from frozen bacteria. Zimmerman says most bacterial pathogens evolved to survive in warmer circumstances. When efforts to grow frozen bacteria in frozen animal and human corpse tissue were made, the bacteria showed no signs of transformation from zombie hibernation to living pathogen. Thus far, they have been shown to be as preserved-but-dead as the host animal and human tissue has been.
However, in the NPR story, there may still be an open book on zombie bacteria. A teacher named Zac Peterson, working with archaeologists digging up an 800-year-old cabin from the permafrost, got a nasty skin infection after handling long-frozen seal tissue at the site. The infection responded to an antibiotic. Its appearance matched something called a “seal finger” infection, though the bacteria were not identified. Peterson said he did not touch any living seals, only the frozen seals.
So, there’s that. There’s no sign of a zombie apocalypse just yet, but if I were one of those lucky people who can raise one eyebrow, mine would be at least at half-mast.