Our analysis of terminal sources resonates with an old hypothesis that in southern China, zoonotic infection from liveanimals markets [28] selling in particular duck-a natural host of influenza [29] -combined with a dense population for sustained viral circulation, could be the main ingredients for the creation of new seasonal influenza variants. In support, two major acute respiratory infections-SARS [30] and H5N1/97 [31, 32] -have been definitively traced back to southern China, with Hong Kong serving as an important sentinel post for the rest of the world. Other influenza pandemics, 1968 H3N2 (Hong Kong) [28] and even as early as 1889 pandemic influenza [33] , have suspected origins in southern China.