Yards and yards of clear plastic sheeting line the cellar floor, dwarfing the corpse: headless, frail, supine. The young bony arms — covered in fine black powder from centuries of immobility in the frozen tundra — are crossed at rest, reminiscent of a ceremonial burial. Camera flashes illuminate the scene. Several dozen scientists stand around the body, murmuring in Russian and English about the find of the day.

How long do you think it was buried? Do you think it’s male or female? How did they get it back to camp? And the pervasive thought: I don’t think we should touch it. He could have died of smallpox.

Smallpox was a vicious disease before its eradication in the 1970s, but the virus is hardy and can survive long-term storage. One such storage unit is the tundra of the high northern latitudes that preserves an unknown number of bodies that could have died from smallpox. Global warming is now rapidly thawing this freezer, increasing the chance that someone could come into contact with a smallpox-infested body, thereby reintroducing the disease.

Smallpox rivals malaria as the most deadly infectious disease ever to affect humans. Throughout history, people looked for ways to combat the disease, priming their immune systems with remedies such as sniffing ground-up scabs or smearing pus into open wounds. The first true vaccine — developed in 1796 by Edward Jenner — was for smallpox.

The variola virus responsible for smallpox, which causes fever, fatigue and pustules that leave deep scars on the skin, decimated the Americas after Columbus landed in the West Indies. The disease similarly ravaged the people of the Arctic, and an estimated 300 million people died from smallpox in the 20th century alone before the World Health Organization’s vaccination campaign was completely effective. The last case from natural exposure was in the late 1970s in Ethiopia.

Today smallpox exists only in highly secure U.S. and Russian laboratories. According to Jonathan Tucker, a senior fellow at the Center for Nonproliferation Studies, “the greatest risk of smallpox infection today is from the continued scientific research with the live virus, as well as from the hypothetical existence of undeclared stocks of the virus that could pose a risk of accidental or deliberate release.” Many scientists agree that an accidental or deliberate release of the virus is a dangerous possibility, especially since vaccinations of the general population ceased in 1972. In response to the attacks on Sept. 11, 2001, the Bush administration ordered the inoculation of U.S. military and health workers so that critical operations would not be affected.

. . .

It was 20 years ago when the headless body was found at a bend in the Kolyma River and brought to camp — at the Northeast Research Station in Cherskii, Siberia. On that day the tundra was changing to red and gold, and longer nights had begun to touch the horizon. Late summer is prosperous near the Arctic Circle: Local fishermen descend on the river to plunder sturgeon, and paleontologists scan the banks by boat and foot for mammoth bones or frozen bodies of ancient musk ox and horses.

Imre Friedmann remembers the day that the body was found. He trudged into the station, finally escaping the plague of swarming mosquitoes, to be told of the body in the cellar. “Everybody avoided handling it,” he recounts in precise, accented English. Friedmann, affiliated with the NASA Ames Research Center, traveled to the Arctic to study the bacteria that thrive in the extreme climate of this region.

Other projects have been similarly affected by the fear of smallpox. Archaeologists halted work in the London crypt Spitalfields in the mid-1980s after finding smallpox scars on a corpse, and a librarian from Santa Fe, N.M., was vaccinated after finding a smallpox scab in a Civil War medical book. In these cases, the virus was no longer viable. But a construction worker in the United Kingdom did contract the disease while demolishing a building that had housed smallpox victims, and researchers in Holland found a live virus in a 13-year-old scab.

Bodies frozen in the north could be even more fertile ground as a reservoir of the virus. Smallpox is resilient when frozen. Louise Parker and James Martel of the Army Corps of Engineers reported that vaccinia, the virus used in the smallpox vaccine, survives short-term freezing and thawing as well as storage at low temperatures. And in the 1950s, U.S. Army scientists found that the variola survived three years of freezing, particularly at very low temperatures.

In the 1980s, a mass grave near Pokhodsk, Siberia, was exposed by a river and local residents demanded testing of the bodies. Researchers took all the necessary precautions of an epidemic: protective gear, antiseptic cleansing and vaccinations. But even though some bodies were well preserved after a hundred years in permafrost, “viable smallpox virus was not detected, but the virus antigen was discovered,” says Sergei Davidov, currently the assistant director of the field station in Cherskii.

Fear of frozen corpses lying beneath the tundra may even be the reason that the United States and Russia maintain stockpiles, according to Donald Henderson. Henderson, an epidemiologist currently at Johns Hopkins University, directed the World Health Organization’s smallpox eradication campaign. After hammering out an agreement between the two countries to reduce smallpox stockpiles, he was “just about ready to take this to the World Heath Assembly when a guy from Britain shows up.” This man was the head of the United Kingdom’s chemical and biological weapons program.

Henderson recalls their conversation.

How could you do that?

How could I do what?

Let me say this: Suppose you have bodies in the tundra? What would we do to protect people — we’ve destroyed the virus.

Henderson explained to the chemist that the possibility of virus frozen in the north has little to do with maintenance of laboratory stockpiles. But the chemist took his concerns to the U.S. Department of Defense, and, according to Henderson, the fear of naturally frozen virus is what led the military to withdraw from the resolution. “I can’t make it up,” he laughs.

Some life does exist in frozen soil and ice. Imre Friedmann, who had been in the research station with the body, points out that “in permafrost we find living bacteria in 3 million-year-old permafrost. So if bacteria survive, I don’t see why viruses don’t survive.” Friedmann is referring to a team from the Russian Academy of Sciences that found bacteria in ancient permafrost. Viruses have also been discovered in old ice cores: Scott Rogers of Bowling Green State University in Ohio found a 140,000-year-old RNA plant pathogen in Greenland.

Taken together — the possibility that viruses survive, the hardiness of smallpox and the expanse of frozen tundra — it seems possible that viable variola could be preserved in permafrost. “If it were going to be anywhere,” Henderson says, “if you were going to find something, [the tundra] would be the likely place.”

Global warming is thawing permafrost. In Siberia, botanists at Tomsk State University estimate that an area twice the size of California has changed from featureless tundra to a lake-dotted, slumped landscape. The decomposition of formerly frozen soil is in turn accelerating global warming because of the release of previously trapped methane gas. The northern Arctic is warming more quickly than other parts of the world, and, according to projections by the National Center for Atmospheric Research in Colorado, the uppermost 10 feet of the Northern Hemisphere’s permafrost may be gone by 2100.

“Obviously the delicate relationship between climate and permafrost is going to have to find new equilibrium,” says Wayne Pollard, a permafrost specialist at McGill University in Montréal.

But what does an accelerated thaw mean for smallpox? Some experts think that climate change reduces the chance of a smallpox reintroduction because the virus cannot survive multiple days unfrozen. To Tucker of the Center for Nonproliferation Studies, “the gradual thawing of the permafrost brought about by global warming [further diminishes] the likelihood of recovering infectious smallpox virus particles from the corpses of victims buried in the Arctic region.”

There is a caveat to this assumption, though. According to Pollard, there are different kinds of permafrost. The ice-rich permafrost is rapidly changing the northern landscape, but dry permafrost, on the other hand, could better preserve a body and the viruses harbored.

“It’s important to say, ‘Never say never,’ with some of these things because it’s like saying life couldn’t have arrived on Earth from an asteroid,” concludes Russell Regnery of the Poxvirus Program at the Centers for Disease Control and Prevention. He thinks that the disease impact from global warming will come from the ooze of tropical diseases such as malaria and leishmaniasis into newly available habitats rather than from the release of pathogens because of permafrost melt.

. . .

The morning after finding the frozen corpse along the Kolyma River, several researchers carried it out of the Cherskii Research Station past a few scraggily evergreens. It was buried that day in 1990, just before the Soviet Union opened. Under normal circumstances, scientists might have examined an old body: one researcher thought the traditional reindeer skin clothing was about 300 years old. But the fear of the unknown — of smallpox — evaporated their intellectual interest.

But fear needs perspective. “These things don’t cough anymore,” says the CDC’s Regnery. Short of people wiping a newly exposed cadaver across their eye, it is hard for him to see how the virus could transfer. Epidemiologist Henderson adds that an outbreak of smallpox would kill people, but it could be contained. Sick people go to bed, and the disease transfers from person to person only when the pustules are obvious. Says Henderson: “There is a lot of docudrama stuff out there that is absolute poppycock.”

Note: Imre Friedmann died in June at the age of 85, after this article had been written.

This story is provided by Scienceline, a project of New York University's Science, Health and Environmental Reporting Program.