Li F C K, Choi B C K, Sly T, Pak A W P
Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, 100 Colonnade Road Ottawa, Ontario, K1A 0K9, Canada.
J Epidemiol Community Health. 2008 Jun;62(6):555-9. doi: 10.1136/jech.2007.064030.
Accurate estimation of the case-fatality (CF) rate, or the proportion of cases that die, is central to pandemic planning. While estimates of CF rates for past influenza pandemics have ranged from about 0.1% (1957 and 1968 pandemics) to 2.5% (1918 pandemic), the official World Health Organization estimate for the current outbreak of H5N1 avian influenza to date is around 60%.
The official estimate of the H5N1 CF rate has been described by some as an over-estimate, with little relevance to the rate that would be encountered under pandemic conditions. The reasons for such opinions are typically: (i) numerous undetected asymptomatic/mild cases, (ii) under-reporting of cases by some countries for economic or other reasons, and (iii) an expected decrease in virulence if and when the virus becomes widely transmitted in humans. Neither current data nor current literature, however, adequately supports these scenarios. While the real H5N1 CF rate could be lower than the current estimate of 60%, it is unlikely that it will be at the 0.1-0.4% level currently embraced by many pandemic plans. We suggest that, based on surveillance and seroprevalence studies conducted in several countries, the real H5N1 CF rate should be closer to 14-33%.
Clearly, if such a CF rate were to be sustained in a pandemic, H5N1 would present a truly dreadful scenario. A concerted and dedicated effort by the international community to avert a pandemic through combating avian influenza in animals and humans in affected countries needs to be a global priority.
准确估计病死率（CF），即病例死亡的比例，是大流行规划的核心。过去流感大流行的病死率估计范围从约0.1%（1957年和1968年大流行）到2.5%（1918年大流行），而世界卫生组织目前对H5N1禽流感疫情的官方估计约为60%。
一些人认为H5N1病死率的官方估计过高，与大流行情况下可能出现的病死率关联不大。产生这种观点的原因通常有：（i）大量未被发现的无症状/轻症病例，（ii）一些国家因经济或其他原因未报告病例，以及（iii）如果病毒在人类中广泛传播，其毒力预计会下降。然而，目前的数据和文献都没有充分支持这些情况。虽然实际的H5N1病死率可能低于目前60%的估计，但不太可能处于许多大流行规划目前所采用的0.1 - 0.4%的水平。我们认为，根据在几个国家进行的监测和血清流行率研究，实际的H5N1病死率应更接近14 - 33%。
显然，如果在大流行中维持这样的病死率，H5N1将呈现出真正可怕的情景。国际社会需要齐心协力，通过在受影响国家防控动物和人类的禽流感来避免大流行，这应成为全球优先事项。
