Since the beginning of the COVID-19 pandemic, multiple variants of concern (VOCs) and variants of interest (VOIs) have been designated by WHO based on their assessed potential for expansion and replacement of prior variants, for causing new waves with increased circulation, and for the need for adjustments to public health actions.
Based on comparisons of antigenic cross reactivity using animal sera, replication studies in experimental models of the human respiratory tract, and evidence from clinical and epidemiological studies in humans, there is consensus among experts in WHO’s Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE) that compared to previous variants, Omicron represents the most divergent VOC seen to date.
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从遗传和抗原角度来看，自出现以来，奥密克戎病毒持续进化，亚谱系范围不断扩大。
Since its emergence, Omicron viruses have continued to evolve genetically and antigenically with an expanding range of sublineages, which so far have all been characterized by properties of evasion of existing population immunity and a preference to infect the upper respiratory tract (versus lower respiratory tract), as compared to pre-Omicron VOCs.
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自2022年2月以来，在所公布的基因序列中，奥密克戎病毒占98%以上。
The Omicron viruses account for over 98% of the publicly available sequences since February 2022 and constitute the genetic background from which new SARS-CoV-2 variants will likely emerge, although the emergence of variants derived from previously circulating VOCs or of completely new variants remains possible.
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奥密克戎病毒是可能出现的SARS-CoV-2新变异株的基因来源。
The previous system classified all Omicronsublineages as part of the Omicron VOC and thus did not have the granularity needed to compare new descendent lineages with altered phenotypes to the Omicron parent lineages (BA.1, BA.2, BA.4/BA.5).
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不过，仍有可能在先前传播的变异株基础上演变出新的变异株或出现全新的变异株。
Therefore, from 15 March 2023, the WHO variant tracking system will consider the classification of Omicron sublineages independently as variants under monitoring (VUMs), VOIs, or VOCs.
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另外，世卫组织正在更新需要关注的变异株和需要留意的变异株的工作定义。
WHO is also updating the working definitions for VOCs and VOIs.
The main update consists in making the VOC definition more specific, to include major SARS-CoV-2 evolutionary steps that require major public health interventions.
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如查阅经更新的定义，请访问世卫组织变异株跟踪网站。
For the updated definitions, please visit the WHO variant tracking website.
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此外，世卫组织今后用希腊字母为需要关注的变异株命名，而不再对需要留意的变异株指定希腊字母名称。
In addition, going forward, WHO will assign Greek labels for VOCs, and will no longer do so for VOIs.