The 1918 influenza virus that killed more than 20-million people worldwide originated from American pigs and is unlike any other known flu bug, say researchers.
Using lung tissue taken at autopsy 79 years ago from an Army private killed by the flu, scientists at the Armed Forces Institute of Pathology made a genetic analysis of the virus and concluded it is unique, though closely related to the "swine" flu.
"This is the first time that anyone has gotten a look at this virus which killed millions of people in one year, making it the worst infectious disease episode ever," said Dr. Jeffery Taubenberger, leader of the Armed Forces Institute team. "It does not match any virus that has been found since."
Although the disease that caused the worldwide epidemic was called "Spanish flu," the virus apparently is a mutation that evolved in American pigs and was spread around the globe by U.S. troops mobilized for World War I, said Taubenberger.
The Army private whose tissue was analyzed contracted the flu at Fort Jackson, S.C. For that reason, Taubenberger and his colleagues suggest in today's issue of the journal Science that the virus be known as Influenza A/South Carolina.
Army doctors in 1918 conducted autopsies on some of the 43,000 servicemen killed by the flu and preserved some specimens in formaldehyde and wax. Taubenberger said his team sorted through 30 specimens before finding enough virus in the private's lung tissue to partially sequence the genes for two key proteins in flu virus.
The 1918 flu pandemic killed at least 21-million worldwide, Taubenberger said. In the United States, about a quarter of the population had the flu and 2 percent to 3 percent died _ some 700,000 people.