美国国家公共电台 NPR--Omicron keeps finding new evolutionary tricks to outsmart our immunity

Omicron keeps finding new evolutionary¹ tricks to outsmart our immunity²

Transcript³

Throughout the pandemic, the virus that causes COVID-19 has been evolving fast, blindsiding the world with one variant⁴ after another.

But the World Health Organization hasn't given a SARS-CoV-2 variant a Greek name in almost a year, a move that's reserved for new variants⁵ that do or could have significant public health impacts, such as being more transmissible or causing more severe disease.

That raises the question: Has the evolution of the virus finally started to ebb⁶, possibly making it more predictable?

The answer — according to a dozen evolutionary biologists, virologists and immunologists interviewed by NPR — is no.

"SARS-CoV-2 is continuing to evolve extremely rapidly," says Trevor Bedford, a computational biologist who studies the evolution of viruses at the Fred Hutchinson Cancer Center in Seattle. "There's no evidence that the evolution is slowing down."

Instead, the most consequential⁷ evolutionary changes have stayed confined to the omicron family, rather than appearing in entirely⁸ new variants.

Whereas alpha, beta, gamma and the other named variants sprouted⁹ new branches on the SARS-CoV-2 family tree, those limbs were dwarfed¹⁰ by the omicron bough¹¹, which is now studded with a plethora¹² of subvariant stems.

"The children of omicron — so the many direct children and cousins within the diverse omicron family — those have displaced each other" as the dominant¹⁴ strains driving the pandemic, says Emma Hodcroft, a molecular¹⁵ epidemiologist at the University of Bern. "But that same family has been dominating" by outcompeting other strains.

The ever-expanding omicron brood has maintained its dominance through what's known as "convergent¹⁶" evolution — when entities¹⁷ independently develop similar traits because of similar environmental pressures, according to Manon Ragonnet-Cronin, who studies viral genetics at the University of Chicago.

"We seem to be seeing for the first time evidence of widescale convergent evolution," Ragonnet-Cronin says. "We have what people are calling a swarm¹⁸ of omicron viruses, which have different ancestries¹⁹ within omicron, but which have the same set of mutations."

Those mutations endow these omicron offspring with the one power they need most right now: the ability to sneak²¹ past the immunity that people have built up from getting infected, vaccinated²², or both.

"When you see convergence in evolution that's evolution's way of saying 'this mutation²⁰ is repeatedly getting selected over and over again because it's really helpful,'" says Jesse Bloom, a computational biologist at the Fred Hutchinson Cancer Center in Seattle.

Those mutations in the virus's spike²³ protein have been increasing its ability to evade²⁴ protective antibodies and continue infecting massive numbers of people.

"This virus is getting a lot of lottery²⁵ tickets if you will. And it looks like, with these new variants, these new mutations are like the jackpot," says Jeremy Kamil, an immunologist at Louisiana State University.

The Centers for Disease Control and Prevention is tracking more than a dozen omicron subvariants right now, including BF.7, BQ.1 and BQ.1.1, some of which appear to be among the most immune-evasive yet.

Fortunately, the immunity people have built up from vaccination²⁶ and infection still appears to be protecting most from serious illness and death.

But the newer highly contagious²⁷ omicron subvariants could help drive yet another surge. They also give the virus many chances to reproduce, mutate and evolve even more.

A family tree still full of surprises?

While all this sounds dire¹³, omicron's long period of dominance is giving some scientists some hope.

The virus could, in one relatively²⁸ optimistic scenario²⁹, keep evolving this way for a long time, drifting in more subtle evolutionary directions like the flu, without sudden shifts in how it behaves that make it more dangerous.

"The fact that we've perhaps stepped out of a phase [in the pandemic] where we're getting completely new viruses from different parts of the tree sweeping³⁰ in and dominating might be a sign that we're moving towards a more kind of stable future for the virus," Hodcroft says.

But that would mean large numbers of people would still catch the virus. Many would still get seriously ill, die, or be left with long COVID. And because the virus is still so new, it's impossible to know how the virus might evolve in the future, experts tell NPR.

"We are literally³¹ dealing³² with a completely novel virus here," says Kristian Andersen, an immunologist at Scripps Research. "We don't know how many other paths this particular virus might have. We just don't know at this stage."

There's no way to rule out, for example, the possibility that a dramatically different variant might emerge yet again, perhaps after simmering inside someone with a compromised immune system that can't drive out the virus. That lets the virus extensively interact with the human immune system and find even more advantageous³³ mutations.

"I guarantee you that there are people who have been persistently³⁴ infected with delta³⁵ and alpha who have some really weird³⁶ combinations of mutations," says Michael Worobey, an evolutionary biologist at the University of Arizona. "And I'm fully³⁷ prepared for a delta-based or alpha-based omicron-like event where one of those zombie viruses that's been cooking away within someone emerges."

1 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

2 immunity   

n.优惠；免除；豁免，豁免权

参考例句：

• The law gives public schools immunity from taxation.法律免除公立学校的纳税义务。
• He claims diplomatic immunity to avoid being arrested.他要求外交豁免以便避免被捕。

3 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

4 variant   

adj.不同的，变异的；n.变体，异体

参考例句：

• We give professional suggestions according to variant tanning stages for each customer.我们针对每位顾客不同的日晒阶段，提供强度适合的晒黑建议。
• In a variant of this approach,the tests are data- driven.这个方法的一个变种，是数据驱动的测试。

5 variants   

n.变体( variant的名词复数 )；变种；变型；（词等的）变体

参考例句：

• Those variants will be preserved in the'struggle for existence". 这些变异将在“生存竞争”中被保留下来。 来自辞典例句
• Like organisms, viruses have variants, generally called strains. 与其他生物一样，病毒也有变种，一般称之为株系。 来自辞典例句

6 ebb   

vi.衰退，减退；n.处于低潮，处于衰退状态

参考例句：

• The flood and ebb tides alternates with each other.涨潮和落潮交替更迭。
• They swam till the tide began to ebb.他们一直游到开始退潮。

7 consequential   

adj.作为结果的，间接的；重要的

参考例句：

• She was injured and suffered a consequential loss of earnings.她受了伤因而收入受损。
• This new transformation is at least as consequential as that one was.这一新的转变至少和那次一样重要。

8 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

9 sprouted   

v.发芽( sprout的过去式和过去分词 )；抽芽；出现；（使）涌现出

参考例句：

• We can't use these potatoes; they've all sprouted. 这些土豆儿不能吃了，都出芽了。 来自《简明英汉词典》
• The rice seeds have sprouted. 稻种已经出芽了。 来自《现代汉英综合大词典》

10 dwarfed   

vt.（使）显得矮小（dwarf的过去式与过去分词形式）

参考例句：

• The old houses were dwarfed by the huge new tower blocks. 这些旧房子在新建的高楼大厦的映衬下显得十分矮小。
• The elephant dwarfed the tortoise. 那只乌龟跟那头象相比就显得很小。 来自《简明英汉词典》

11 bough   

n.大树枝，主枝

参考例句：

• I rested my fishing rod against a pine bough.我把钓鱼竿靠在一棵松树的大树枝上。
• Every bough was swinging in the wind.每条树枝都在风里摇摆。

12 plethora   

n.过量，过剩

参考例句：

• Java comes with a plethora of ready-made types.Java配套提供了数量众多的现成类型。
• A plethora of new operators will be allowed to enter the market.大批新的运营商将获准进入该市场。

13 dire   

adj.可怕的，悲惨的，阴惨的，极端的

参考例句：

• There were dire warnings about the dangers of watching too much TV.曾经有人就看电视太多的危害性提出严重警告。
• We were indeed in dire straits.But we pulled through.那时我们的困难真是大极了，但是我们渡过了困难。

14 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。

15 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

16 convergent   

adj.会聚的

参考例句：

• A curved-inwards wall has a convergent effect on wall spray.凹型壁面对碰壁喷雾有聚集作用。
• If a sequence is not convergent,it is divergent.如果一个序列不收敛，我们称它发散。

17 entities   

实体对像； 实体，独立存在体，实际存在物( entity的名词复数 )

参考例句：

• Our newspaper and our printing business form separate corporate entities. 我们的报纸和印刷业形成相对独立的企业实体。
• The North American continent is made up of three great structural entities. 北美大陆是由三个构造单元组成的。

18 swarm   

n.(昆虫)等一大群；vi.成群飞舞；蜂拥而入

参考例句：

• There is a swarm of bees in the tree.这树上有一窝蜜蜂。
• A swarm of ants are moving busily.一群蚂蚁正在忙碌地搬家。

19 ancestries   

n.祖先，世系( ancestry的名词复数 )

参考例句：

• All patients and control ancestries were measured ABO blood type. 所有的患者和对照组个体均进行ABO血型检测。 来自互联网
• Our point here is that all ancestries have all experiences therein. 这里我们的重点是，其中所有祖先都经历了所有事件。 来自互联网

20 mutation   

n.变化，变异，转变

参考例句：

• People who have this mutation need less sleep than others.有这种突变的人需要的睡眠比其他人少。
• So far the discussion has centered entirely around mutation in the strict sense.到目前为止，严格来讲，讨论完全集中于围绕突变问题上。

21 sneak   

vt.潜行(隐藏,填石缝)；偷偷摸摸做；n.潜行；adj.暗中进行

参考例句：

• He raised his spear and sneak forward.他提起长矛悄悄地前进。
• I saw him sneak away from us.我看见他悄悄地从我们身边走开。

22 vaccinated   

[医]已接种的，种痘的，接种过疫菌的

参考例句：

• I was vaccinated against tetanus. 我接种了破伤风疫苗。
• Were you vaccinated against smallpox as a child? 你小时候打过天花疫苗吗？

23 spike   

n.长钉，钉鞋；v.以大钉钉牢，使...失效

参考例句：

• The spike pierced the receipts and held them in order.那个钉子穿过那些收据并使之按顺序排列。
• They'll do anything to spike the guns of the opposition.他们会使出各种手段来挫败对手。

24 evade   

vt.逃避，回避；避开，躲避

参考例句：

• He tried to evade the embarrassing question.他企图回避这令人难堪的问题。
• You are in charge of the job.How could you evade the issue?你是负责人，你怎么能对这个问题不置可否？

25 lottery   

n.抽彩；碰运气的事，难于算计的事

参考例句：

• He won no less than ￡5000 in the lottery.他居然中了5000英镑的奖券。
• They thought themselves lucky in the lottery of life.他们认为自己是变幻莫测的人生中的幸运者。

26 vaccination   

n.接种疫苗，种痘

参考例句：

• Vaccination is a preventive against smallpox.种痘是预防天花的方法。
• Doctors suggest getting a tetanus vaccination every ten years.医生建议每十年注射一次破伤风疫苗。

27 contagious   

adj.传染性的，有感染力的

参考例句：

• It's a highly contagious infection.这种病极易传染。
• He's got a contagious laugh.他的笑富有感染力。

28 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

29 scenario   

n.剧本，脚本；概要

参考例句：

• But the birth scenario is not completely accurate.然而分娩脚本并非完全准确的。
• This is a totally different scenario.这是完全不同的剧本。

30 sweeping   

adj.范围广大的，一扫无遗的

参考例句：

• The citizens voted for sweeping reforms.公民投票支持全面的改革。
• Can you hear the wind sweeping through the branches?你能听到风掠过树枝的声音吗？

31 literally   

adv.照字面意义，逐字地；确实

参考例句：

• He translated the passage literally.他逐字逐句地翻译这段文字。
• Sometimes she would not sit down till she was literally faint.有时候，她不走到真正要昏厥了，决不肯坐下来。

32 dealing   

n.经商方法，待人态度

参考例句：

• This store has an excellent reputation for fair dealing.该商店因买卖公道而享有极高的声誉。
• His fair dealing earned our confidence.他的诚实的行为获得我们的信任。

33 advantageous   

adj.有利的；有帮助的

参考例句：

• Injections of vitamin C are obviously advantageous.注射维生素C显然是有利的。
• You're in a very advantageous position.你处于非常有利的地位。

34 persistently   

ad.坚持地；固执地

参考例句：

• He persistently asserted his right to a share in the heritage. 他始终声称他有分享那笔遗产的权利。
• She persistently asserted her opinions. 她果断地说出了自己的意见。

35 delta   

n.（流的）角洲

参考例句：

• He has been to the delta of the Nile.他曾去过尼罗河三角洲。
• The Nile divides at its mouth and forms a delta.尼罗河在河口分岔，形成了一个三角洲。

36 weird   

adj.古怪的，离奇的；怪诞的，神秘而可怕的

参考例句：

• From his weird behaviour,he seems a bit of an oddity.从他不寻常的行为看来，他好像有点怪。
• His weird clothes really gas me.他的怪衣裳简直笑死人。

37 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。