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| Where is Pi? | 还没有到“派”(Pi)？ |
| Last year, the World Health Organization began assigning Greek letters to worrying new variants of the coronavirus. The organization started with Alpha and swiftly worked its way through the Greek alphabet in the months that followed. When Omicron arrived in November, it was the 13th named variant in less than a year. | 去年，世界卫生组织开始用希腊字母给引发担忧的新冠病毒新变异株命名。他们从希腊字母阿尔法(Alpha)开始，并在随后的几个月中迅速更迭。在不到一年时间里，于11月启用的“奥密克戎”(Omicron)已经是第13个得到命名的变异株。 |
| But 10 months have passed since Omicron’s debut, and the next letter in line, Pi, has yet to arrive. | 但是距离奥密克戎的首次出现已经过去了10个月，而下一个字母派还没有启用。 |
| That does not mean SARS-CoV-2, the coronavirus that causes Covid-19, has stopped evolving. But it may have entered a new stage. Last year, more than a dozen ordinary viruses independently transformed into major new public health threats. But now, all of the virus’s most significant variations are descending from a single lineage: Omicron. | 这并不意味着导致2019冠状病毒病的冠状病毒SARS-CoV-2已经停止进化。但它可能已经进入了一个新的阶段。去年，十几种普通病毒独立转变为新的重大公共卫生威胁。但是现在，该病毒所有最重要的变异都来自同一个谱系：奥密克戎。 |
| “Based on what’s being detected at the moment, it’s looking like future SARS-CoV-2 will evolve from Omicron,” said David Robertson, a virologist at the University of Glasgow. | 格拉斯哥大学的病毒学家大卫·罗伯逊说：“根据目前检测到的情况，似乎未来的SARS-CoV-2将从奥密克戎进化而成。” |
| It’s also looking like Omicron has a remarkable capacity for more evolution. One of the newest subvariants, called BA.2.75.2, can evade immune responses better than all earlier forms of Omicron. | 而且，看起来奥密克戎也有非凡的继续进化的能力。最新的亚型变异株BA.2.75.2比以往所有奥密克戎变体更善于逃避免疫反应。 |
| For now, BA.2.75.2 is extremely rare, making up just .05 percent of the coronaviruses that have been sequenced worldwide in the past three months. But that was once true of other Omicron subvariants that later came to dominate the world. If BA.2.75.2 becomes widespread this winter, it may blunt the effectiveness of the newly authorized boosters from Moderna and Pfizer. | BA.2.75.2目前还极为罕见，仅占过去三个月全球测序的新冠病毒的0.05%。但那些后来在全世界占据主导地位的其他奥密克戎亚型也曾如此。如果BA.2.75.2在今年冬天蔓延，可能会使莫德纳和辉瑞公司新授权的加强针的有效性降低。 |
| Every time SARS-CoV-2 replicates inside of a cell, it might mutate. On rare occasions, a mutation might help SARS-CoV-2 replicate faster. Or it might help the virus evade antibodies from previous bouts of Covid. | 每次SARS-CoV-2在细胞内复制时都可能发生突变。在极少数情况下，突变可能有助于SARS-CoV-2更快地复制。或者可能会帮助病毒逃避之前感染新冠病毒后产生的抗体。 |
| Such a beneficial mutation might become more common in a single country before fading away. Or it might take over the world. | 在消亡之前，这种有利于病毒生存的突变可能会在某个国家变得更加普遍。或者可能会蔓延到全世界。 |
| At first, SARS-CoV-2 followed the slow and steady course that scientists had expected based on other coronaviruses. Its evolutionary tree gradually split into branches, each gaining a few mutations. Evolutionary biologists kept track of them with codes that were useful but obscure. No one else paid much attention to the codes, because they made little difference to how sick the viruses made people. | SARS-CoV-2的进化起初是一个缓慢而稳定的过程，符合科学家基于其他冠状病毒的预期。它的进化树逐渐分裂成分支，每个分支都获得了一些突变。进化生物学家用有意义但晦涩难懂的代号来追踪它们。除了他们之外，没人关注这些代号，因为它们不太影响病毒致人患病的程度。 |
| But then one lineage, initially known as B.1.1.7, defied expectations. When British scientists discovered it, in December 2020, they were surprised to find it bore a unique sequence of 23 mutations. Those mutations allowed it to spread much faster than other versions of the virus. | 但后来的一个谱系打破了预期，它最初被称为B.1.1.7。当英国科学家在2020年12月发现它时，他们惊讶地发现它带有包含23个突变的独特序列。这些突变使它比其他版本的病毒传播得更快。 |
| Within a few months, several other worrying variants came to light around the world — each with its own combination of mutations, each with the potential to spread quickly and cause a surge of deaths. To make it easier to communicate about them, the W.H.O. came up with its Greek system. B.1.1.7 became Alpha. | 几个月之内，世界各地又出现了其他几个令人担忧的变体——每一个都有自己的突变组合，每一个都可能迅速传播并导致死亡人数激增。为了易于交流，世卫组织选择了希腊字母系统。B.1.1.7成了阿尔法。 |
| Different variants experienced varying levels of success. Alpha came to dominate the world, whereas Beta took over only in South Africa and a few other countries before petering out. | 不同的变体经历了不同程度的成功。阿尔法开始在世界占据主导地位，而“贝塔”(Beta)只在南非和其他几个国家蔓延，然后逐渐消亡。 |
| What made the variants even more puzzling was that they arose independently. Beta did not descend from Alpha. Instead, it arose with its own set of new mutations from a different branch of the SARS-CoV-2 tree. The same held true for all the Greek-named variants, up to Omicron. | 更加令人费解的是，这些变体是独立出现的。贝塔并非来自阿尔法。相反，它是由来自SARS-CoV-2进化树的不同分支的一组新突变产生的。所有以希腊命名的变体，一直到奥密克戎，都是如此。 |
| It’s likely that most of these variants got their mutations by going into hiding. Instead of jumping from one host to another, they created chronic infections in people with weakened immune systems. | 这些变体中的大多数很可能是通过藏匿而获得突变的。它们没有从一个宿主外溢到另一个宿主，而是在免疫系统较弱的人身上造成慢性感染。 |
| Unable to mount a strong attack, these victims harbored the virus for months, allowing it to accumulate mutations. When it eventually emerged from its host, the virus had a startling range of new abilities — finding new ways to invade cells, weaken the immune system and evade antibodies. | 由于无法发动强大的攻击，这些病毒在患者体内藏匿了数月，积累了突变。当病毒最终从宿主中出现时，已经具有一系列惊人的新能力——找到侵入细胞、削弱免疫系统和逃避抗体的新方法。 |
| “When it gets out, it’s like an invasive species,” said Ben Murrell, a computational biologist at the Karolinska Institute in Stockholm. | “它出现时就像一个入侵物种，”斯德哥尔摩卡罗林斯卡研究所的计算生物学家本·默勒尔说。 |
| Omicron did particularly well in this genetic lottery, gaining more than 50 new mutations that helped it find new routes into cells and to infect people who had been vaccinated or previously infected. As it spread around the world and caused an unprecedented spike in cases, it drove most other variants to extinction. | 奥密克戎在这种基因抽奖中手气格外好，获得了50多个新突变，帮助它找到了进入细胞的新途径，并感染了接种过疫苗或之前感染过的人。随着它在世界范围内传播并造成前所未有的病例激增，其他大多数变种逐渐消亡。 |
| “The genetic innovations seen in Omicron were far more profound, as if it was a new species rather than just a new strain,” said Darren Martin, a virologist at the University of Cape Town. | “在奥密克戎中看到的基因创新要深刻得多，就好像它是一个新品种，而不仅仅是一个新毒株，”开普敦大学的病毒学家达伦·马丁说。 |
| But it soon became clear that the name “Omicron” hid a complex reality. After the original Omicron virus evolved in the fall of 2021, its descendants split into at least five branches, known as BA.1 through BA.5. | 但很快人们就发现，“奥密克戎”这个名字隐藏了一个复杂的现实。在2021年秋天最初的奥密克戎病毒进化后，它的后代分裂成至少五个分支，被称为BA.1到BA.5。 |
| Over the next few months, the subvariants took turns rising to dominance. BA.1 went first, but it was soon outcompeted by BA.2. Each one was distinct enough from the others to evade some of the immunity of its predecessors. By this summer, BA.5 was on the rise. | 在接下来的几个月里，这些亚型轮流占据主导地位。BA.1抢先一步，但很快就被BA.2打败。每一种都足够独特，从而逃避了前一种的某些免疫力。到今年夏天，BA.5正在崛起。 |
| The U.S. Food and Drug Administration responded by inviting vaccine makers to produce booster shots that included a BA.5 protein along with one from the original version of the virus. Those boosters are now rolling out to the public, at a time when BA.5 is causing 85 percent of all Covid cases in the United States. | 作为回应，美国食品和药物管理局邀请疫苗制造商生产包括BA.5蛋白和一种来自病毒原始版本蛋白的加强针。目前，在美国85%的新冠病例是由BA.5引起的，而这些加强针正在向公众推广。 |
| But BA.5 could be fading in the rearview mirror by winter, scientists said. Omicron has continued to evolve — likely by sometimes jumping among hosts, and sometimes hiding for months in one of them. | 但科学家们说，BA.5可能会在冬季之前逐渐消失。奥密克戎一直在进化——可能有时在宿主之间跳跃，有时在其中一个宿主当中隐藏数月。 |
| Since these new lineages belong to Omicron, they haven’t gotten a Greek letter of their own. But that doesn’t mean they’re just a slight twist on the original. Antibodies that could latch onto earlier forms of Omicron fare poorly against the newer ones. | 由于这些新的世系都属于奥密克戎，它们并没有属于自己的希腊字母。但这并不意味着它们只是在原版的基础上稍加改动。能够对抗早期奥密克戎的抗体在新形式的奥密克戎面前表现不佳。 |
| “They could arguably have been given different Greek letters,” Dr. Robertson said. | “他们其实可以被赋予不同的希腊字母，”罗伯逊说。 |
| BA.2.75.2 is among the newest of Omicron’s grandchildren, identified just last month. It’s also the most evasive Omicron yet, according to Dr. Murrell. In lab experiments, he and his colleagues tested BA.2.75.2 against 13 monoclonal antibodies that are either in clinical use or in development. It evaded all but one of them, bebtelovimab, made by Eli Lilly. | 上个月刚刚被确认的BA.2.75.2是奥密克戎最新的孙辈之一。据莫雷尔说，这也是迄今为止最难以捉摸的奥密克戎。在实验室实验中，他和同事测试了BA.2.75.2对抗13种临床使用或开发中的单克隆抗体。除了礼来公司生产的Bebtelovimab外，它逃过了所有抗体。 |
| They also tested the antibodies from recent blood donors in Sweden. BA.2.75.2 did substantially better at escaping those defenses than other Omicron subvariants did. | 他们还测试了最近瑞典献血者的抗体。BA.2.75.2在规避这些防御方面明显优于其他奥密克戎亚型。 |
| The researchers posted their study online on Friday. Researchers at Peking University reached similar conclusions in a study posted the same day. Both have yet to be published in a scientific journal. | 研究人员于周五在网上发布了他们的研究。北京大学的研究人员在同一天发布的一项研究中得出了类似的结论。这两项研究都尚未在科学期刊上发表。 |
| Dr. Murrell cautioned that scientists have yet to run experiments that will show the effectiveness of BA.5 booster shots against BA.2.75.2. He suspected that getting a big supply of BA.5 antibodies would provide some protection, especially against severe disease. | 莫雷尔警告说，科学家们还没有进行实验，来证明BA.5加强针对BA.2.75.2的有效性。他怀疑获得大量的BA.5抗体能提供一些保护，特别是对重症的保护。 |
| “It’s still important, but we’ll have to wait for the data to come out to see exactly what the magnitude of the boosting effect is,” Dr. Murrell said. | “这仍然很重要，但我们必须等待数据出来，才能确切了解这种抗体究竟有多大作用，”莫雷尔说。 |
| There’s no reason to expect that BA.2.75.2 will be the end of the evolutionary line. As immunity builds to previous versions of Omicron, new versions will be able to evolve that can evade it. | 没有理由指望BA.2.75.2会是进化路线的终点。随着对以前版本的奥密克戎的免疫力的增强，新版本还将进化出能够躲避免疫力的病毒。 |
| “I don’t think it’s going to hit a wall in the mutational space,” said Daniel Sheward, a postdoctoral researcher at the Karolinska Institute and co-author on the new study. | “我不认为它会在突变空间中撞上一堵墙，”卡罗林斯卡学院的博士后研究员、这项新研究的合著者丹尼尔·谢沃德说。 |
| Lorenzo Subissi, an infectious disease expert with the W.H.O., said that the organization was not giving Greek letters to lineages like BA.2.75.2 because they are much like the original Omicron viruses. For example, it appears that all Omicron lineages use a distinctive route to get into cells. As a result, it is less likely to lead to severe infections but possibly better able to spread than previous variants. | 世界卫生组织的传染病专家洛伦佐·苏比西说，该组织没有给BA.2.75.2这样的变异赋予希腊字母，因为它们与最初的奥密克戎病毒非常相似。例如，似乎所有的奥密克戎系变异株都使用一种独特的途径进入细胞。因此，它不太可能导致严重的感染，但可能比以前的变异株更容易传播。 |
| “W.H.O. only names a variant when it is concerned that additional risks are being created that require new public health action,” Dr. Subissi said. But he did not rule out a Pi in our future. | “世界卫生组织只有在担心会产生额外的风险，需要采取新的公共卫生行动时，才会为一个变异株命名，”苏比西说。但他不排除未来会出现派毒株。 |
| “This virus still remains largely unpredictable,” he said. | “这种病毒在很大程度上仍然不可预测，”他说。 |
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