The authors hypothesize that concerns about the Fort Dix outbreak stimulated a flurry of research on H1N1 viruses in 1976, which led to an accidental release and re-emergence of the previously extinct virus a year later. The re-emerged 1977 H1N1 strain has continued to circulate among humans as seasonal flu for the past 32 years.

Although originally traced to Mexico, the exact physical origins of the 2009 H1N1 pandemic virus are unknown. Because the current strain shares common ancestry with older flu strains, it is possible that portions of the population may have partial immunity to the new pandemic virus.

The authors also go on to explain that the danger posed by a virus isn't based solely on its lethality, but also on its transmissibility, which is the ability to jump from animals to humans and to survive by mutating to adapt to its new human host. H1N1 influenza viruses have demonstrated this ability throughout their history.

"Studying the history of emergence and evolution of flu viruses doesn't provide us with a blueprint for the future, but it does reveal general patterns, and this kind of information is critical if we are to be as prepared as possible," said Dr. Burke.

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