The Spanish flu of 1918 is most often compared to the current strain, because scientists have discovered that the pathogen of that scourge originated among birds, and just like the strain presently raging in Southeast Asia, mutated and was transmitted to humans.
而被拿來與這次禽流感相提並論的，是 1918 年爆發的西班牙大流感，因為科學家研究發現，那場大流感病毒源自鳥類，與現今在東南亞肆虐的禽流感一樣，都是先在鳥類身上發生，突變後傳染給人類。