Evolution and Prediction of Influenza Viruses

根据禽流感在鸟类、动物和人类中的流行病学研究结果，我们提出了A/Hong Kong/68（H3N2）毒株血凝素（HA）基因的引入途径，即从迁徙鸭中流行的h3流感病毒传入中国南方的家鸭，然后传入与H2N2亚洲流感病毒发生基因重组的猪，从而产生新的大流行毒株A/Hong Kong/68（H3N2）。为了提供有关北部地区水禽筑巢点甲型流感病毒分布情况的信息，1991年和1992年夏季在阿拉斯加进行了病毒学调查。从鸟类粪便样本2579份（包括1313只鸭子、646只鹅、6只天鹅、7只鸭鸭和7只海鸥）中分离出75种流感病毒和82种副粘病毒。其中，H3N8病毒14株，H4N6病毒47株，H8N2病毒1株，H10N2病毒1株，H10N7病毒11株，H10N9病毒1株。在鸭的巢点，病毒的抗原亚型和分离率不同。1992年，还采集了湖水样本进行病毒分离。在23份水样中，从不同湖泊分离出两株h4n6病毒。这支持了流感病毒在自然界中延续的机制的概念，即病毒随鸭子的粪便排出，并在冬季保存在北部地区的冰冻湖水中。用一组单克隆抗体对H3流感病毒分离物的血凝素（HA）进行抗原分析，发现它们与a /Hong Kong/68（H3N2）流感病毒的血凝素（HA）密切相关。本研究结果还表明，流感病毒在鸭群的巢区内得到维持和保存。在鸭窝地区持续监测鸭体内的流感病毒，必须为预测可能出现的新的人类大流行性流感病毒株提供有用的信息。

On the basis of the results of epidemiological studies of influenza in birds, animals, and humans, we have proposed the route of introduction of the hemagglutinin(HA) gene of the A/Hong Kong/68(H3N2) strain, i.e., from a H3influenza virus circulating in migratory ducks to domestic ducks in Southern China, then to pigs where genetic reassortment occurred with the H2N2 Asian influenza virus to produce the new pandemic strain, A/Hong Kong/68(H3N2).To provide information on the distribution of influenza A viruses in waterfowls at their nesting points in the northern territory, virological survey was carried out in Alaska in summer of 1991 and 1992. From 2,579 fecal samples of birds comprizing 1,913 ducks, 646 geese, 6 swans, 7 dunlins, and 7 gulls, 75 influenza viruses and 82 paramyxoviruses were isolated. Most of the influenza virus isolates were obtained from those of ducks, consisting of 14 H3N8, 47 H4N6, 1 H8N2, 1 H10N2, 11 H10N7, and 1 H10N9 viruses. The antigenic subtypes and isolation rates of the viruses were different in the nesting points of ducks. In 1992, lake water samples were also collected for virus isolation. Out of 23 water samples two H4N6virus strains were isolated from different lakes. This support the notion of the mechanism of perpetuation of influenza viruses in nature, that viruses shed with feces from ducks and have been preserved in frozen lake water in winter in northern territory.Antigenic analysis of the hemagglutinin(HA) of H3 influenza virus isolates using a panel of monoclonal antibodies showed that they were closely related to that of the A/Hong Kong/68(H3N2) influenza virus. The present results also indicate that influenza viruses are maintained and conserved in duck population in their nesting areas. Continued surveillance of influenza viruses in ducks in their nesting areas must provide useful information for prediction of possible new human pandemic influenza virus strains.