即使作为奥米克龙新冠肺炎变体继续席卷全球，科学家们现在正在监测一种新的奥米克隆突变，被称为BA.2。
世界卫生组织坚持认为BA.2不是“令人担忧的变种”，这意味着目前没有证据表明这种新的亚变种会恶化新冠肺炎病毒的传播、疾病的严重程度或疫苗的效力以及公共卫生努力，如掩盖和社会距离。
全球BA.2的数量正在上升，至少有40个国家向全球变异体追踪数据库报告了病例，但这种次变异体在丹麦和英国迅速传播，丹麦最近的病例中几乎有一半归因于BA.2。
这种变异病毒已经在美国几个州被发现，华盛顿州周一确认了两起病例。
虽然自2021年11月以来已发现超过8，000例BA.2病例，但不清楚BA.2源自何处。尽管第一批序列是从菲律宾提交的，但从欧洲到南亚，各地都发现了大量病例。
鉴于数字不断上升，卫生保健组织，如世卫组织，正在要求科学家与奥米克隆分开观察和研究这种新的亚变异体，看看它是否有不同的表现。
英国卫生安全局新冠肺炎事件负责人米拉·钱德博士在事先准备好的讲话中说:“病毒进化和变异是病毒的天性，因此可以预计，随着疫情疫情的发展，我们将继续看到新的变种出现。”。“到目前为止，没有足够的证据来确定BA.2是否会导致比Omicron BA.1更严重的疾病，但数据有限。”
新冠肺炎子变量的演变并不新鲜。delta变体也有几个亚变体，但科学家称它们都是delta。然而，由于几个国家的学生人数不断增加，英国文学学士学位已经赢得了自己的称号。
奥德林·约瑟夫/美联社
文件-一名医务工作者在疫苗接种过程中准备注射Moderna疫苗.
哈佛大学波士顿儿童医院首席创新官、美国广播公司医学记者约翰·布朗斯坦博士说，尽管它被称为“隐形”奥米克隆变体，但新的亚变体“无论是通过快速测试还是聚合酶链反应，都绝对可以通过传统的监控机制被检测到”。
传统的新冠肺炎测试可以显示阳性或阴性结果，但它们不能确定具体的变异。为此，科学家需要进行额外的基因测序。方便的是，omicron变体有一个特殊的基因特征，使科学家能够快速轻松地确定样本是否是omicron。
新的BA.2亚变异体没有这种特征，这意味着科学家们不能再使用这种捷径——尽管他们仍然可以使用基因测序技术来识别亚变异体。正因为如此，BA.2次变体有时被称为“隐形”变体。但是对于普通大众来说，传统的新冠肺炎测试仍然可以检测出新的次变分。
最终，虽然科学家和公共卫生官员敦促继续进行研究和监测，但专家表示，没有什么理由担心。
布朗斯坦说:“从公共卫生的角度来看，BA.2很重要，但它不会在此刻从根本上改变我们对人口影响的看法。“在对临床相关性做出任何声明之前，需要做更多的工作来了解严重程度、突破性感染和免疫接种。”
布朗斯坦补充说:“尽管理解在奥米克隆家族中，有一个潜在的更容易传播的子谱系很重要，但这不一定会引起恐慌。
Scientists monitoring new omicron subvariant BA.2
Even as the omicronCOVID-19 variantcontinues to sweep the globe, scientists are now monitoring a newmutation of omicron, dubbed BA.2.
The World Health Organization maintains that BA.2 is not a "variant of concern," meaning there is no current evidence to suggest this new subvariant will worsen COVID-19 transmission, illness severity, or efficacy of vaccines and public health efforts like masking and social distancing.
BA.2 numbers around the world are rising, with at least 40 countries reporting cases to a global variant tracking database, but the subvariant has spread rapidly in Denmark and the UK, with almost half of recent cases in Denmark attributed to BA.2.
The subvariant has already been detected in several U.S. states, with Washington State confirming two cases Monday.
While over 8,000 BA.2 cases have been identified since November 2021, it is unclear where BA.2 originated. Even though the first sequences were submitted from the Philippines, numerous cases have since been detected in various places, from Europe to South Asia.
Given the rising numbers, health care organizations, like the WHO, are asking scientists to watch and study the new subvariant separately from omicron, to see if it behaves differently.
"It is the nature of viruses to evolve and mutate, so it's to be expected that we will continue to see new variants emerge as the pandemic goes on," said Dr. Meera Chand, the COVID-19 incident director at the UK Health Security Agency, in prepared remarks. "So far, there is insufficient evidence to determine whether BA.2 causes more severe illness than Omicron BA.1, but data is limited."
The evolution of COVID-19 subvariants is not new. The delta variant also had several subvariants, but scientists referred to all of them as delta. BA.2, however, has earned its own designation due to rising numbers across several nations.
Although it's been called the "stealth" omicron variant, the new subvariant, "can absolutely be detected through traditional surveillance mechanisms whether through rapid testing or PCR," said Dr. John Brownstein, chief innovation officer at Harvard University's Boston Children's Hospital and ABC Medical Correspondent.
Conventional COVID-19 tests can show a positive or a negative result, but they can't determine specific variants. For that, scientists need to do additional genetic sequencing. Conveniently, the omicron variant has a particular genetic signature that allows scientists to quickly and easily determine if the sample is omicron or not.
The new BA.2 subvariant does not have that feature, meaning scientists can no longer use this shortcut -- though they can still identify the subvariant using genetic sequencing technology. Because of this, the BA.2 subvariant has sometimes been referred to as the "stealth" variant. But for the general public, conventional COVID-19 tests will still work to detect the new subvariant.
Ultimately, while scientists and public health officials are urging continued research and surveillance, experts say there is little reason to worry.
"BA.2 is important from a public health perspective, but it doesn't fundamentally change at this moment, how we think about the impact in the population," Brownstein said. "A lot more work needs to be done to understand severity, breakthrough infections, and immunizations before you can make any statement about clinical relevance."
"While it's important to understand that in the family of omicron, there is a sub-lineage that is potentially more transmissible, it's not necessarily a cause for panic," Brownstein added.
