It does not match any virus that has been found since. Science is publishing the study today. 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 hemagglutinin and neuraminidase, two of the key proteins in flu virus. The finding supports a widespread theory flu viruses from swine are the most virulent for humans.
Most experts believe flu viruses reside harmlessly in birds, where they are genetically stable.
Occasionally. a virus from birds will infect pigs. The swine immune system attacks the virus, forcing it to change genetically to survive. The result is a new virus. When this new bug is spread to humans, it can be devastating, said Thaubenberger. Knowing what the 1918 virus was like may help researchers learn why it was so deadly and virulent, he said.