ABSTRACT
I. Introduction It may be somewhat of a paradox to consider influenza as an emerging pathogen, with yearly epidemics and worldwide pandemics dating back at least a century. These “old” manifestations of influenza continue into the 21st century with continual adaptation by the influenza virus necessitating yearly changes in our vaccination strategies. However, avian influenza has recently emerged as a “new” threat, with concern that this avian virus may convert to the next great pandemic virus, similar to the devastating 1917 to 1918 “Spanish” influenza pandemic that resulted in over 50 million deaths. When the next new pandemic will occur, how severe it will be, and where it will originate from, depend, in part, on how the new pandemic strain “borrows” genetic elements from both zoonotic and human strains. How “askew” this goes, in large part, will be determined by several factors that cannot be predicted.
