The H9N2 influenza virus is endemic in poultry. We report its occurrence in live-poultry markets, fair-trade markets and poultry farms in the Shanghai region between September 2006 and December 2010. An analysis of partial sequences of the HA, NA, PB1, PB2 and NP genes of eleven distinct H9N2 isolates revealed that all carried an RSSR motif at the cleavage site of HA, diagnostic of low pathogenicity in chickens. A phylogenetic analysis indicated that these isolates are derived from the lineage represented by Duck/HK/Y280/97, but they have evolved a range of reassortments. Their PB1 and NP sequences resembled those of H5N1 strains, indicating a hybrid origin involving both H9 and H5 strains. The HA and NA sequences present in all eleven isolates resembled those of the Duck/HK/Y280/97-like lineage. Infection by H9N2 is commonplace in Shanghai live-poultry markets, allowing the viruses to have evolved rapidly.
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机译：H9N2流感病毒是家禽的地方病。我们报告了其在2006年9月至2010年12月间在上海地区的活禽市场，公平交易市场和禽场中发生的情况。分析了11种不同的H9N2分离株的HA，NA，PB1，PB2和NP基因的部分序列揭示了所有这些都在HA的切割位点带有RSSR基序，诊断出鸡的低致病性。系统发育分析表明，这些分离株是由Duck / HK / Y280 / 97代表的谱系衍生的，但是它们已经进化出一系列重排。它们的PB1和NP序列与H5N1菌株相似，表明杂种起源涉及H9和H5菌株。所有11种分离物中都存在的HA和NA序列与Duck / HK / Y280 / 97样谱系相似。 H9N2感染在上海活禽市场中很普遍，这使病毒得以迅速发展。
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