WASHINGTON -- A frozen corpse and preserved samples from victims of the 1918 flu epidemic that killed millions of people worldwide show the virus resembled the common swine flu, scientists reported Monday.
Tissue samples from three people who died in the epidemic have provided enough genetic material to allow researchers to sequence, or map, one key gene of the virus, a team from the US Armed Forces Institute of Pathology wrote in the Proceedings of the National Academy of Sciences.
"The existing strain to which the 1918 sequences are most closely related is A/Sw/Iowa/30, the oldest classical swine-flu strain," the scientific team, led by Ann Reid and Jeffrey Taubenberger, wrote.
"The influenza pandemic of 1918 was exceptionally severe, killing 20 to 40 million people worldwide, with unusually high death rates among young, healthy adults," it wrote.
Researchers have been eager to discover what made the 1918 strain of flu so different -- and so deadly.
Scientists also wanted to know where the virus originated because that can help doctors understand how best to fight the disease. But scientists investigating the 1918 flu were stymied in part by the difficulty of finding viable samples from people who have been dead for more than eight decades.
Last year, a team tried to get samples from people buried on the Norwegian island of Spitzbergen, but they found the bodies were buried above the permafrost and the tissues were not well enough preserved to provide good genetic samples.
The Armed Forces Institute of Pathology team used samples from the body of an Alaskan Inuit who was buried in permafrost on the Seward Peninsula and tissue preserved in formaldehyde from a 21-year-old soldier who died at Fort Jackson, South Carolina, and a 30-year-old who died at Camp Upton, New York.
They managed to sequence the entire gene from the samples for hemagglutinin, a protein the influenza virus uses to infect the cells scientists look at first to determine a flu strain.
Influenza is so troublesome because it mutates regularly. Scientists believe it originates in birds and sometimes spreads directly to humans, as in the case of the "bird flu" in Hong Kong that killed six people in 1997 and led to the mass slaughter of birds in the territory.
More often, the virus passes from birds to pigs, where it takes on characteristics that make it easier to pass to humans.
The Reid-Taubenberger team said it is not yet clear whether the 1918 virus came to people straight from birds or passed through pigs first -- or whether it passed from people to pigs.
They noted that there had been an outbreak in the spring of a mild flu, followed by an outbreak in the autumn among pigs, then the killer epidemic in people. "This sequence of events supports the theory that the 1918 influenza spread from humans to swine," they concluded.
Copyright© 1999 Reuters Limited.
