Influenza
Influenza
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DOI：
10.1016/s0891-5520(05)70406-2
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发表时间：
1998-03-01
影响因子：
4.4
通讯作者：
Fukuda, K
中科院分区：
文献类型：
--
作者：
Cox, NJ;Fukuda, K
流感病毒易于发生快速和不可预测的抗原变化，这使得流感在新发和复发疾病中占有突出地位。(29 50，81）历史记载表明，引起人类高度传染性、发热性、急性呼吸道疾病的流感病毒已经存在了几个世纪。(48)几乎每年都发生严重程度不一的流行病。流感的大流行通常比每年一次的流行具有更广泛和更显著的影响，其发生的时间间隔也是不可预测的。在本世纪，由流感病毒引起的三次最显著的事件是始于1918年的“西班牙”流感大流行、1957年的“亚洲”流感，以及最近的1968年的“香港”流感。在每一次大流行中，新型流感病毒迅速而普遍地席卷地球仪，并在所有年龄组中引起疾病。(78)每一次大流行都伴随着高发病率、严重的社会混乱和巨大的经济损失。此外，西班牙流感大流行与年轻人和以前健康的成年人中相对较高的病死率有关。这种独特的死亡模式产生了深刻的医学、社会和政治后果。(13)虽然许多人不认为这是真正的大流行，但1977年重新出现的甲型H1N1流感病毒（“俄罗斯”流感）也值得注意，因为这些病毒迅速席卷地球仪，并在20岁以下的人群中造成相当大的发病率。（78）流感病毒复制和进化的两个特征解释了这些病毒在流行病学上的成功。首先，在表面蛋白、血凝素（HA）和神经氨酸酶（NA）中存在相对快速和不可预测的抗原变化（抗原漂移）。抗原漂移是流感病毒以大流行形式出现并在人类中建立后持续进化的一部分。随着人群中大流行毒株的抗体水平上升，流行的流感病毒必须改变抗原才能生存。抗原性漂移使个体对新毒株易感，因为抗原性漂移的流感病毒能够逃避先前流行毒株的抗体的中和。每年的流行病都发生在大流行的间隔期，因为人群中有足够数量的个体对抗原变异株易感。第二，人类中出现了新的甲型流感病毒（抗原转变）。当某些动物流感病毒（通常只感染禽类或猪宿主，与目前在人类中流行的流感病毒无关）传播给人类时，就会发生抗原性转变。有证据表明，新的大流行毒株的出现可能发生在人类和动物流感病毒之间的基因重组之后，或者通过动物毒株直接传播给人类。(80因此，抗原性转变定义为在人群中出现含有新HA或新HA和NA的新流感病毒，所述新HA或新HA和NA在免疫学上不同于近几十年来在人类中传播的流感病毒。当这些新型病毒发生人际传播并导致大量免疫易感人群患病时，就会发生大流行。
The propensity of influenza viruses to undergo rapid and unpredictable antigenic change has given influenza a prominent place among emerging and reemerging diseases.(29, 50, 81) Historical accounts suggest that influenza viruses, which cause a highly contagious, febrile, acute respiratory illness in humans, have been around for centuries.(48) Epidemics of various severity have occurred almost annually. Pandemics of influenza, which generally have had a more widespread and dramatic impact than annual epidemics, have occurred unpredictably at irregular intervals.The three most dramatic events caused by influenza viruses during this century were the pandemics of "Spanish" influenza beginning in 1918, the 1957 "Asian" influenza, and most recently, the 1968 "Hong Kong" influenza. In each pandemic, novel influenza viruses swept rapidly and pervasively around the globe and caused disease in all age groups.(78) Each pandemic was associated with high rates of morbidity, considerable social disruption, and substantial economic losses. In addition, the Spanish influenza pandemic was associated with a relatively high case-fatality rate in young and previously healthy adults. This unique pattern of mortality had profound medical, social, and political consequences.(13) Although not considered a true pandemic by many,(38) the reemergence in 1977 of influenza A (H1N1) viruses ("Russian" influenza) is also notable because these viruses swept rapidly around the globe and caused considerable morbidity among individuals under 20 years of age.(78)Two features of influenza virus replication and evolution account for the epidemiologic success of these viruses. First, there is relatively rapid and unpredictable antigenic change (antigenic drift) in the surface proteins, hemagglutinin (HA), and neuraminidase (NA). Antigenic drift occurs as part of the continuing evolution of influenza viruses after they emerge in pandemic form and become established in humans. As antibody levels to the pandemic strain rise within the human population, the circulating influenza viruses must change antigenically to survive. Antigenic drift renders an individual susceptible to new strains because the antigenically drifted influenza viruses are able to escape neutralization by antibody to previously circulating strains. Annual epidemics occur during the interpandemic period because sufficient numbers of individuals in the population become susceptible to the antigenically variant strain.Second, there is the emergence of novel influenza A viruses in humans (antigenic shift). Antigenic shift occurs when certain animal influenza viruses, which normally infect only avian or swine reservoirs and are unrelated to the influenza viruses currently circulating in humans, are transmitted to humans. Evidence suggests that emergence of novel pandemic strains may occur either after genetic reassortment between human and animal influenza viruses or, alternatively, via direct transmission of an animal strain to humans.(80, 81) Thus, antigenic shift is defined as the appearance in the human population of a new influenza virus containing a novel HA or novel HA and NA that are immunologically distinct from those of the influenza viruses that have been circulating in man in recent decades. A pandemic takes place when human-to-human transmission of these novel viruses occurs and leads to disease in a large and immunologically susceptible human population.