It was like a scene out of a horror movie: In an unused storage facility in an old Food and Drug Administration lab, officials stumbled across a box containing decades-old vials labeled "variola."
The variola virus, better known as smallpox, cost some 300 million lives in the 20th century alone. Smallpox was eradicated in 1975, thanks to heroic vaccination and containment efforts by the World Health Organization and other scientific agencies. Today, the only known samples of that deadly virus are officially kept in just two laboratories in the world, one in the U.S. and another in Russia.
When FDA officials found the vials earlier this week, they immediately cleared the area and called in experts from the Centers for Disease Control. The CDC confirmed that the vials do indeed contain traces of variola's DNA, though tests to find out whether the viruses are still live—that is, if they can take up residence in tissue—are still underway. As the CDC writes, "If viable smallpox is present, [the World Health Organization] will be invited to witness the destruction of these smallpox materials, as has been the precedent for other cases where smallpox samples have been found outside of the two official repositories."
Is there a chance, though, that more smallpox samples are lurking somewhere in the world?
As Michael Lane, one of the researchers responsible for the smallpox eradication effort back in the 1970s, told the BBC Future, "There’s no way to prove a negative.”
In other words, there's a good chance other smallpox samples are stuck at the back of some forgotten freezer or hoarded away in someone's basement. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, corroborated this view on USA Today:
Osterholm says it's not totally surprising to find smallpox in an unused storage area. Still, he says it's likely that other labs will look a bit more carefully to see if they also have any aging vials with surprising labels.
"The freezers of the microbiology labs of the world are a lot like the trunks in your attic. When you open them up, sometimes you are surprised," Osterholm says. "Most people have already gone through their freezers, but some freezers get missed."
The good news, though, is that even if smallpox was somehow unleashed on a population of people today, it would probably be easily contained, Osterholm told USA Today. The virus does not spread especially quickly, and its transmission requires contact with an infected person. Vaccines also exist, and more could be manufactured. As BBC Future writes, "We beat smallpox once and we could beat it again."