专家将禽流感强毒株的出现和传播归因于工业化农业中大规模工厂化养殖的极度拥挤、不卫生和紧张的环境。
(The emergence and spread of virulent strains of avian influenza has been attributed by experts to the intensely overcrowded, unsanitary, and stressful conditions that often characterize large-scale factory farming in industrialized agriculture.)