美国国家公共电台 NPR--Long COVID may be due to the virus sticking around after infection, researchers say

Long COVID may be due to the virus sticking around after infection, researchers say

Transcript¹

A growing body of evidence points to the idea that the coronavirus can stick around long after an initial infection. Some researchers think that may be a major driver of long COVID.

LEILA FADEL, HOST:

What's behind long COVID? That's the question frustrated² patients and scientists have been working to answer for several years, and now it seems one possible explanation for the condition is gaining traction³. NPR's Will Stone has more on those looking to solve long COVID's mystery.

WILL STONE, BYLINE⁴: Brent Palmer's research on long COVID started before that phrase meant anything. Palmer had some friends who'd caught the virus while on a ski trip. It was March 2020. And they'd returned home with this new illness. Palmer works at the University of Colorado, where he studies how the immune system responds to infectious diseases. So this was too good to pass up. He started collecting their blood and was intrigued⁵ by one person in particular.

BRENT PALMER: I was up there maybe a month and a half after they had SARS-CoV-2, and she was still complaining of heart palpitations, chest pains, some difficulty breathing.

STONE: Palmer was analyzing⁶ part of the immune system's arsenal⁷ known as T cells, and, he noticed, unlike the others, her blood still had a very high percentage of these immune cells aimed at the virus.

PALMER: So I just kind of shelved that and thought, well, that's interesting.

STONE: He says, typically, T cells reach very high levels during the acute infection, and over time, they drop off. So he was surprised as he began looking at the T cells of more and more long COVID patients well after they had been infected.

PALMER: These individuals had frequencies that were 100-fold higher in some cases than the individuals that didn't have any sort of persistent⁸ symptoms.

STONE: Those with long COVID also had higher levels of systemic inflammation that was associated with worse lung function. It had been months since their infection, but it was like their immune system was still fighting the virus, which raised the question.

PALMER: Even despite the fact they test negative in a nasal swab, the - is the virus still persisting in the lung? Is it persisting in some other organ?

STONE: Many scientists working on long COVID have wondered the same thing over the past few years. Maybe the virus isn't entirely⁹ gone. Maybe there are viral reservoirs hiding in the body. And with each new piece of evidence, the case for this is getting stronger. Take the findings of David Walt at Harvard Medical School. His team detected proteins from the coronavirus, mostly the spike¹⁰ protein, in the blood of some long COVID patients up to a year after their infection.

DAVID WALT: And the only place it could be released from is from, you know, some sort of reservoir, some source of virus that continues to spew these proteins out.

STONE: It was a relatively¹¹ small study, and Walt says as they've looked at more long COVID patients, it appears only about 20% have viral proteins in their blood. But for those who do...

WALT: We think that this is, you know, to some extent, a smoking gun for the presence of, you know, a persistent, active viral infection.

STONE: Then there are all the places in the body where scientists have unearthed¹² evidence of the virus, like in biopsies of the gut¹³ or in the stool of people who'd had COVID months earlier. Dr. Dan Chertow at the National Institutes of Health led a painstaking¹⁴ autopsy¹⁵ study of people who'd had COVID.

DAN CHERTOW: We found virus in over 30 different cell types in tissues really throughout the body.

STONE: Essentially¹⁶, all the major organs, like the lungs, kidneys, liver, heart and throughout the brain.

CHERTOW: It, you know, provides definitive¹⁷ evidence that the virus is capable of spreading to parts all over the body, that it is capable of persisting all over the body.

STONE: In one case, they found genetic¹⁸ material from the virus had persisted for 200 days. And in another...

CHERTOW: In an individual that died relatively early, within two weeks of their initial illness, we were able to culture live virus in the brain.

STONE: He says you can only take so much from this study. After all, it wasn't focused on long COVID, and the people tended to be older and sicker. But Chertow says their findings do provide strong biological plausibility¹⁹ that viral reservoirs may play a role. So where does all of this evidence leave us in the hunt to uncover the roots of long COVID? Microbiologist Amy Proal sums it up this way.

AMY PROAL: No one thinks that every long COVID patient has the exact same thing happening, but we do think that of the research that has come out recently, that reservoir of the virus in tissue ranks at the top of what might be happening to a good number of patients.

STONE: Proal is president of the nonprofit PolyBio Research Foundation, which is working with scientists to advance this theory of viral persistence²⁰.

PROAL: Does it persist more in certain body sites over others? If it does persist in one body site, does it have a different mechanism²¹ of how it sticks around there? Like, all these nuances of how it's sticking around, we need further research on.

STONE: Mohamed Abdel-Mohsen at The Wistar Institute says scientists now need to draw a clear line from viral reservoirs to the long COVID symptoms. He says it's possible the body's immune response to the virus or parts of the virus is behind some symptoms.

MOHAMED ABDEL-MOHSEN: A chronic²² reaction to something could lead to immune dysfunction and inflammation. Anything happening in a long period of time can cause our immune system to be, quote, "exhausted²³ and dysfunctional."

STONE: Now, there are many theories about what's contributing to long COVID. For example, Abdel-Mohsen wants to know if viral reservoirs in the gut are responsible for bacteria and fungi²⁴ leaking into the bloodstream. Scientists are also looking at the role of autoimmunity or damaged tissue or tiny blood clots²⁵. The list goes on. Abdel-Mohsen says it's important to realize that some of these theories are not mutually exclusive.

ABDEL-MOHSEN: Each one of them could happen independently and can lead to a problem to our immune system, but it can all lead to each other.

STONE: Figuring out which treatments work for long COVID can also help untangle what's going on here. There's keen interest in using antivirals, like the COVID drug Paxlovid, because it might help extinguish any residual²⁶ virus. A trial at Stanford expects to have results on that later this year. But some people aren't waiting for that data.

SCOTT LEDUC: I did see some dramatic benefit.

STONE: Scott LeDuc has dealt with long COVID since early in the pandemic. About three months ago, he found a doctor who was willing to prescribe him Paxlovid for 15 days.

LEDUC: All of a sudden, I was able to go for longer walks. You know, I'm starting to push myself a little bit. I was actually starting to introduce some light jogging.

STONE: After struggling for so long, he says it was euphoric.

LEDUC: I truly felt well, that I was almost back to my previous self.

STONE: It didn't entirely last, though. Within a few weeks, LeDuc found himself backsliding. But he says the medication did give him a new, improved baseline, and it also gave him something else - a bit of hope.

Will Stone, NPR News.

(SOUNDBITE OF BLACK TAFFY'S "GERALDINE")

1 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。

2 frustrated   

adj.挫败的，失意的，泄气的v.使不成功( frustrate的过去式和过去分词 )；挫败；使受挫折；令人沮丧

参考例句：

• It's very easy to get frustrated in this job. 这个工作很容易令人懊恼。
• The bad weather frustrated all our hopes of going out. 恶劣的天气破坏了我们出行的愿望。 来自《简明英汉词典》

3 traction   

n.牵引；附着摩擦力

参考例句：

• I'll show you how the traction is applied.我会让你看如何做这种牵引。
• She's injured her back and is in traction for a month.她背部受伤，正在作一个月的牵引治疗。

4 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

5 intrigued   

adj.好奇的，被迷住了的v.搞阴谋诡计(intrigue的过去式)；激起…的兴趣或好奇心；“intrigue”的过去式和过去分词

参考例句：

• You've really intrigued me—tell me more! 你说的真有意思—再给我讲一些吧！
• He was intrigued by her story. 他被她的故事迷住了。

6 analyzing   

v.分析；分析( analyze的现在分词 )；分解；解释；对…进行心理分析n.分析

参考例句：

• Analyzing the date of some socialist countries presents even greater problem s. 分析某些社会主义国家的统计数据，暴露出的问题甚至更大。 来自辞典例句
• He undoubtedly was not far off the mark in analyzing its predictions. 当然，他对其预测所作的分析倒也八九不离十。 来自辞典例句

7 arsenal   

n.兵工厂，军械库

参考例句：

• Even the workers at the arsenal have got a secret organization.兵工厂工人暗中也有组织。
• We must be the great arsenal of democracy.我们必须成为民主的大军火库。

8 persistent   

adj.坚持不懈的，执意的；持续的

参考例句：

• Albert had a persistent headache that lasted for three days.艾伯特连续头痛了三天。
• She felt embarrassed by his persistent attentions.他不时地向她大献殷勤，使她很难为情。

9 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。

10 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。

11 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。

12 unearthed   

出土的（考古）

参考例句：

• Many unearthed cultural relics are set forth in the exhibition hall. 展览馆里陈列着许多出土文物。
• Some utensils were in a state of decay when they were unearthed. 有些器皿在出土时已经残破。

13 gut   

n.[pl.]胆量；内脏；adj.本能的；vt.取出内脏

参考例句：

• It is not always necessary to gut the fish prior to freezing.冷冻鱼之前并不总是需要先把内脏掏空。
• My immediate gut feeling was to refuse.我本能的直接反应是拒绝。

14 painstaking   

adj.苦干的；艰苦的，费力的，刻苦的

参考例句：

• She is not very clever but she is painstaking.她并不很聪明，但肯下苦功夫。
• Through years of our painstaking efforts,we have at last achieved what we have today.大家经过多少年的努力，才取得今天的成绩。

15 autopsy   

n.尸体解剖；尸检

参考例句：

• They're carrying out an autopsy on the victim.他们正在给受害者验尸。
• A hemorrhagic gut was the predominant lesion at autopsy.尸检的主要发现是肠出血。

16 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。

17 definitive   

adj.确切的，权威性的；最后的，决定性的

参考例句：

• This book is the definitive guide to world cuisine.这本书是世界美食的权威指南。
• No one has come up with a definitive answer as to why this should be so.至于为什么该这样，还没有人给出明确的答复。

18 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

19 plausibility   

n. 似有道理, 能言善辩

参考例句：

• We can add further plausibility to the above argument. 我们可以在上述论据之外，再进一步增添一个合理的论据。
• Let us consider the charges she faces, and the legal plausibility of those charges. 让我们考虑一下她面临的指控以及这些指控在法律上的可信性。

20 persistence   

n.坚持，持续，存留

参考例句：

• The persistence of a cough in his daughter puzzled him.他女儿持续的咳嗽把他难住了。
• He achieved success through dogged persistence.他靠着坚持不懈取得了成功。

21 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

22 chronic   

adj.(疾病)长期未愈的，慢性的；极坏的

参考例句：

• Famine differs from chronic malnutrition.饥荒不同于慢性营养不良。
• Chronic poisoning may lead to death from inanition.慢性中毒也可能由虚弱导致死亡。

23 exhausted   

adj.极其疲惫的，精疲力尽的

参考例句：

• It was a long haul home and we arrived exhausted.搬运回家的这段路程特别长，到家时我们已筋疲力尽。
• Jenny was exhausted by the hustle of city life.珍妮被城市生活的忙乱弄得筋疲力尽。

24 fungi   

n.真菌，霉菌

参考例句：

• Students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
• The lawn was covered with fungi.草地上到处都是蘑菇。

25 clots   

n.凝块( clot的名词复数 )；血块；蠢人；傻瓜v.凝固( clot的第三人称单数 )

参考例句：

• When you cut yourself, blood clots and forms a scab. 你割破了，血会凝固、结痂。 来自《简明英汉词典》
• Milk clots when it turns sour. 奶变酸就凝块。 来自《现代英汉综合大词典》

26 residual   

adj.复播复映追加时间；存留下来的，剩余的

参考例句：

• There are still a few residual problems with the computer program.电脑程序还有一些残留问题。
• The resulting residual chromatism is known as secondary spectrum.所得到的剩余色差叫做二次光谱。