PRESTO, Japan Science and Technology Agency, Saitama, Japan and Theoretical Epidemiology, University of Utrecht, Yalelaan 7, Utrecht, 3584 CL, The Netherlands.
Expert Rev Respir Med. 2010 Jun;4(3):329-38. doi: 10.1586/ers.10.24.
When the pandemic influenza A (H1N1) 2009 virus emerged, one of the early priorities was to estimate its virulence. This is measured by the case-fatality ratio (CFR), the proportion of deaths from influenza among the total number of cases. Epidemiological studies in the very early stages of the pandemic estimated the confirmed CFR (cCFR), using confirmed cases as the denominator, to be approximately 0.5%. However, later studies estimated the symptomatic CFR (sCFR) as approximately 0.05% of all medically attended symptomatic cases. Although subjective, the virulence of influenza A (H1N1) 2009 can be perceived as mild. Further epidemiological investigations showed that both the cCFR and sCFR varied greatly by age and risk group. When assessing the efficacy of a specific intervention in reducing the risk of influenza-related death, particular care is required regarding the inclusion criteria and in matching age and underlying conditions between patients with, and without, the intervention.
当甲型 H1N1 流感大流行病毒出现时，早期的重点之一是估计其毒力。这是通过病死率（CFR）来衡量的，即流感总病例中死亡的比例。在大流行的早期阶段，使用确诊病例作为分母的流行病学研究估计确诊病死率（cCFR）约为 0.5%。然而，后来的研究估计了有症状的病死率（sCFR），即所有接受医学治疗的有症状病例中约为 0.05%。尽管是主观的，但甲型 H1N1 流感的毒力可以被认为是轻微的。进一步的流行病学调查显示，cCFR 和 sCFR 因年龄和风险组而异。在评估特定干预措施降低与流感相关的死亡风险的效果时，需要特别注意纳入标准，并在接受和未接受干预的患者之间匹配年龄和基础疾病。
