No one knows why the great influenza pandemic of 1918 was the most virulent of all time. A spring outbreak in the American Midwest had by year’s end spread to every corner of the globe. It left as many as 40 million people dead—and among them were American soldiers who carried it to Europe on their way to battle in World War I. (Photo shows patients in a U.S. Army field hospital, Luxembourg, 1918.)
One was an Army private who fell victim to the flu at age 21. Though he did not survive, his lung tissue did, encased in paraffin wax and stored at the Armed Forces Institute of Pathology in Washington, D.C. Last March molecular pathologist Jeffery Taubenberger and his colleagues at the institute announced that they had succeeded in getting the first direct look at the 1918 virus. Using the polymerase chain reaction—a method of amplifying tiny pieces of genetic material—they managed to extract flu virus rna from the soldier’s preserved lung.
That genetic fingerprint disproved a major hypothesis about the 1918 pandemic. It had been thought that the virus might have hopped into humans directly from birds. Coincidentally, it has recently been shown that such transmission really can occur: in May an avian virus infected and killed a three-year-old Hong Kong boy. Although the boy’s death has alarmed public health officials, it appears to be a freak case, says Taubenberger—and not at all what happened in the 1918 pandemic.
Instead his analysis shows that the 1918 flu strain was more closely related to a pig virus than to an avian virus, although it had a touch of both. Indeed, it supports the theory that pigs—which can be infected by avian and human flu strains as well as by their own—are dangerous mixing vessels that give rise to new strains lethal to humans.
Unfortunately, Taubenberger hasn’t yet figured out what made the 1918 strain so deadly, although he is still trying. If we could learn something about why the virus in 1918 was so lethal, he says, it would help us predict when an influenza virus with that kind of ability would emerge again. And if a virus arose with those similar features, it could be recognized and a huge effort could be mounted to vaccinate people against it.