School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
Am J Epidemiol. 2013 Apr 15;177(8):834-40. doi: 10.1093/aje/kws314. Epub 2013 Mar 3.
One measure of the severity of a pandemic influenza outbreak at the individual level is the risk of death among people infected by the new virus. However, there are complications in estimating both the numerator and denominator. Regarding the numerator, statistical estimates of the excess deaths associated with influenza virus infections tend to exceed the number of deaths associated with laboratory-confirmed infection. Regarding the denominator, few infections are laboratory confirmed, while differences in case definitions and approaches to case ascertainment can lead to wide variation in case fatality risk estimates. Serological surveillance can be used to estimate the cumulative incidence of infection as a denominator that is more comparable across studies. We estimated that the first wave of the influenza A(H1N1)pdm09 virus in 2009 was associated with approximately 232 (95% confidence interval: 136, 328) excess deaths of all ages in Hong Kong, mainly among the elderly. The point estimates of the risk of death on a per-infection basis increased substantially with age, from below 1 per 100,000 infections in children to 1,099 per 100,000 infections in those 60-69 years of age. Substantial variation in the age-specific infection fatality risk complicates comparison of the severity of different influenza strains.
衡量个体层面大流行性流感爆发严重程度的一个指标是新型病毒感染者的死亡风险。然而，在估计分子和分母时存在一些复杂情况。关于分子，与流感病毒感染相关的超额死亡的统计估计往往超过与实验室确认感染相关的死亡人数。关于分母，很少有感染得到实验室确认，而病例定义和病例确定方法的差异会导致病死率风险估计值的广泛差异。血清学监测可用于估计作为分母的累积感染发生率，这在不同研究中更具可比性。我们估计，2009 年甲型 H1N1pdm09 流感病毒的第一波疫情与香港所有年龄段约 232 例（95%置信区间：136，328）超额死亡有关，主要发生在老年人中。基于每例感染的死亡风险的点估计值随着年龄的增长而大幅增加，从儿童中每 10 万例感染不到 1 例增加到 60-69 岁人群中每 10 万例感染 1099 例。特定年龄的感染病死率的巨大差异使得比较不同流感株的严重程度变得复杂。
