The National Institutes of Health scientists say they also have created a technique for identifying antibodies that neutralize that deadly virus, a tool that could help contain future pandemic flu strains.
The findings are important to understanding and preventing the recurrence of the H1N1 influenza virus that caused the 1918 pandemic, and for protecting against virulent flu strains in the future, including the H5N1 avian flu virus.
"Understanding why this influenza virus was so deadly is an extremely important question," said NIAID Director Dr. Anthony Fauci "By building upon earlier research where scientists successfully reconstructed the 1918 pandemic flu strain, Dr. Nabel and his colleagues have demonstrated that this virus is vulnerable to intervention.
The 1918-1919 influenza pandemic was the most deadly flu outbreak in modern history, killing 50 million or more people worldwide.
The study -- led by Dr. Gary Nabel, director of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases -- appears online in the Proceedings of the National Academy of Sciences.