Department of Viroscience, Erasmus Medical Centre, Rotterdam, Netherlands; Artemis Research Institute for One Health in Europe, Utrecht, Netherlands.
Department of Viroscience, Erasmus Medical Centre, Rotterdam, Netherlands.
Lancet. 2014 Dec 6;384(9959):2077-81. doi: 10.1016/S0140-6736(13)62425-3. Epub 2014 Apr 25.
Zoonotic influenza viruses that are a few mutations away from pandemic viruses circulate in animals, and can evolve into airborne-transmissible viruses in human beings. Paradoxically, such viruses only occasionally emerge in people; the four influenza pandemics that occurred in the past 100 years were caused by zoonotic viruses that acquired efficient transmissibility. Emergence of a pandemic virus in people can happen when transmissible viruses evolve in individuals with zoonotic influenza and replicate to titres allowing transmission. We postulate that this step in the genesis of a pandemic virus only occasionally occurs in human beings, because the immune response triggered by zoonotic influenza virus also controls transmissible mutants that emerge during infection. Therefore, an impaired immune response might be needed for within-host emergence of a pandemic virus and replication to titres allowing transmission. Immunocompromised individuals--eg, those with comorbidities, of advanced age, or receiving immunosuppressive treatment--could be at increased risk of generating transmissible viruses and initiating chains of human-to-human infection.
人畜共患流感病毒在动物中循环，其与大流行病毒仅有少数突变，可在人类中进化为空气传播可传染的病毒。矛盾的是，此类病毒偶尔在人群中出现；过去 100 年发生的四次流感大流行是由获得高效传播能力的人畜共患病毒引起的。当具有人畜共患流感的个体中传播性病毒进化并复制到允许传播的滴度时，就可能在人群中出现大流行病毒。我们假设，由于由人畜共患流感病毒引发的免疫反应也控制了在感染期间出现的可传播突变体，因此这种大流行病毒起源的步骤在人类中偶尔发生。因此，大流行病毒在宿主内的出现以及复制到允许传播的滴度可能需要受损的免疫反应。免疫功能低下的个体（例如合并症患者、高龄患者或接受免疫抑制治疗的患者）可能有更高的风险产生可传播的病毒并引发人与人之间的感染链。
