Like genetic mutations, epigenetic changes can pass from one generation of cells to the next. 就像基因突变一样，外遗传改变可以从这一代细胞传给下一代细胞。
Today infectious disease experts recognize that an avian flu virus could genetically change enough to trigger a human pandemic. 现在传染病学家了解到，禽流感病毒的遗传改变，足以引起人类间的大流行。
