Most deaths in the 1918 influenza pandemic were due not to the virus alone but to common bacterial infections that took advantage of victims' weakened immune systems, according to two new studies that could change the nation's strategy against the next pandemic.

"We have to realize that it isn't just antivirals that we need," said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases and coauthor of one study. "We need to make sure that we're prepared to treat people with antibiotics," said Fauci, whose study will be released online this month by the Journal of Infectious Diseases.

In both studies, scientists analyzed a trove of historical documents from around the world, examining firsthand accounts, medical records and autopsy reports.