Emergence of multiple genotypes of H5N1 avian influenza viruses in Hong Kong SAR

Although A/Hong Kong/156/97 (H5N1/97)-like viruses associated with the “bird flu” incident in Hong Kong SAR have not been detected since the slaughter of poultry in 1997, its putative precursors continue to persist in the region. One of these, Goose/Guangdong/1/96 (H5N1 Gs/Gd)-like viruses, reassorted with other avian viruses to generate multiple genotypes of H5N1 viruses that crossed to chickens and other terrestrial poultry from its reservoir in geese. Whereas none of these recent reassortants had acquired the gene constellation of H5N1/97, these events provide insight into how such a virus may have been generated. The recent H5N1 reassortants readily infect and kill chicken and quail after experimental infection, and some were associated with significant mortality of chickens within the poultry retail markets in Hong Kong. Some genotypes are lethal for mice after intra-nasal inoculation and spread to the brain. On this occasion, the early detection of H5N1 viruses in the retail, live poultry markets led to preemptive intervention before the occurrence of human disease, but these newly emerging, highly pathogenic H5N1 viruses provide cause for pandemic concern.

尽管自1997年宰杀家禽后，未再检测到与香港特别行政区（Hong Kong SAR）“禽流感”事件相关的A/香港/156/97（H5N1/97）类病毒，但该病毒的推测前体仍持续在该区域存续。其中一类为鹅/广东/1/96（H5N1 Gs/Gd）类病毒，它们与其他禽源病毒发生基因重配，产生了多种基因型的H5N1病毒；这些病毒从其自然宿主鹅的储存库中溢出，感染鸡只及其他陆生家禽。尽管这些近期重配株均未获得H5N1/97的完整基因构成，但这些事件为解析此类病毒的潜在生成机制提供了关键线索。近期的H5N1重配株在实验感染条件下可高效感染并致死鸡与鹌鹑，部分毒株还曾导致香港活禽零售市场内的鸡只出现显著死亡。部分基因型的病毒经鼻内接种后可对小鼠致死，并可扩散至脑部。此次事件中，科研人员在活禽零售市场中及早检测到H5N1病毒，从而在人类病例出现前实施了预防性干预，但这些新出现的高致病性H5N1病毒仍引发了人们对流感大流行的高度担忧。