Emerging and Re-emerging Infectious Diseases in Animals, Research Unit, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.
Virol J. 2010 Sep 16;7:233. doi: 10.1186/1743-422X-7-233.
In January and November 2008, outbreaks of avian influenza have been reported in 4 provinces of Thailand. Eight Influenza A H5N1 viruses were recovered from these 2008 AI outbreaks and comprehensively characterized and analyzed for nucleotide identity, genetic relatedness, virulence determinants, and possible sites of reassortment. The results show that the 2008 H5N1 viruses displayed genetic drift characteristics (less than 3% genetic differences), as commonly found in influenza A viruses. Based on phylogenetic analysis, clade 1 viruses in Thailand were divided into 3 distinct branches (subclades 1, 1.1 and 1.2). Six out of 8 H5N1 isolates have been identified as reassorted H5N1 viruses, while other isolates belong to an original H5N1 clade. These viruses have undergone inter-lineage reassortment between subclades 1.1 and 1.2 and thus represent new reassorted 2008 H5N1 viruses. The reassorted viruses have acquired gene segments from H5N1, subclade 1.1 (PA, HA, NP and M) and subclade 1.2 (PB2, PB1, NA and NS) in Thailand. Bootscan analysis of concatenated whole genome sequences of the 2008 H5N1 viruses supported the reassortment sites between subclade 1.1 and 1.2 viruses. Based on estimating of the time of the most recent common ancestors of the 2008 H5N1 viruses, the potential point of genetic reassortment of the viruses could be traced back to 2006. Genetic analysis of the 2008 H5N1 viruses has shown that most virulence determinants in all 8 genes of the viruses have remained unchanged. In summary, two predominant H5N1 lineages were circulating in 2008. The original CUK2-like lineage mainly circulated in central Thailand and the reassorted lineage (subclades 1.1 and 1.2) predominantly circulated in lower-north Thailand. To prevent new reassortment, emphasis should be put on prevention of H5N1 viruses circulating in high risk areas. In addition, surveillance and whole genome sequencing of H5N1 viruses should be routinely performed for monitoring the genetic drift of the virus and new reassorted strains, especially in light of potential reassortment between avian and mammalian H5N1 viruses.
2008 年 1 月和 11 月，泰国 4 个省报告了禽流感疫情。从这 2008 年的 AI 疫情中分离出 8 株甲型流感 H5N1 病毒，并对其进行了全面的核苷酸同源性、遗传关系、毒力决定因素和可能的重组位点分析。结果表明，2008 年 H5N1 病毒显示出遗传漂移特征（不到 3%的遗传差异），这在流感病毒中很常见。基于系统进化分析，泰国的 clade 1 病毒分为 3 个不同的分支（亚群 1、1.1 和 1.2）。8 株 H5N1 分离株中有 6 株被鉴定为重组 H5N1 病毒，而其他分离株属于原始 H5N1 群。这些病毒在亚群 1.1 和 1.2 之间发生了谱系间重组，因此代表了新的重组 2008 H5N1 病毒。重组病毒从 H5N1、亚群 1.1（PA、HA、NP 和 M）和亚群 1.2（PB2、PB1、NA 和 NS）获得了基因片段。对 2008 年 H5N1 病毒全长基因组序列的 Bootscan 分析支持了亚群 1.1 和 1.2 病毒之间的重组位点。基于对 2008 年 H5N1 病毒最近共同祖先时间的估计，病毒的潜在遗传重组点可以追溯到 2006 年。对 2008 年 H5N1 病毒的遗传分析表明，病毒所有 8 个基因中的大多数毒力决定因素都保持不变。总之，2008 年有两种主要的 H5N1 谱系在传播。原始 CUK2 样谱系主要在泰国中部传播，重组谱系（亚群 1.1 和 1.2）主要在泰国北部低地传播。为防止新的重组，应重点预防高危地区 H5N1 病毒的传播。此外，应常规进行 H5N1 病毒的监测和全基因组测序，以监测病毒的遗传漂移和新的重组株，特别是在禽源和哺乳动物 H5N1 病毒之间可能发生重组的情况下。
