But that might be changing because these conditions could have a surprising cause, common infections like the flu.

但這種情況可能正在發生變化，因為這些病症可能有一個令人驚訝的原因，那就是像流感這樣的普通感染。

In other words, these diseases may not be something we have to accept as part of getting older.

換句話說，這些疾病可能並不是我們必須接受的老齡化的一部分。

We might be able to prevent them.

我們或許可以阻止他們。

Now to be clear, the flu virus does not suddenly give people Alzheimer's, it gives people the flu.

現在要明確的是，流感病毒不會突然讓人患上老年痴呆症，它只會讓人患上流感。

And Alzheimer's is not infectious.

阿爾茨海默氏症不會傳染。

You can't catch Alzheimer's the way you can catch the flu or mono.

你不能像感染流感或單核細胞增多症那樣感染老年痴呆症。

That's because Alzheimer's, Parkinson's, and dementia all belong to a family of chronic diseases that are caused by a buildup of protein gunk in our brain and nervous system.

這是因為阿爾茨海默氏症、帕金森氏症和痴呆症都屬於慢性疾病家族，它們都是由大腦和神經系統中的蛋白質垃圾堆積引起的。

They're called neurodegenerative diseases, or NDDs.

它們被稱為神經退行性疾病，或 NDDs。

But when researchers look back into history, they start to see some odd trends.

但是，當研究人員回顧歷史時，他們開始發現一些奇怪的趨勢。

A few years after big virus outbreaks like the 1918 flu pandemic, they would keep seeing surges in Parkinsonism, or symptoms like Parkinson's.

像 1918 年流感大流行這樣的病毒大爆發幾年後，他們會發現帕金森病或類似帕金森病的症狀不斷激增。

Since then, a constellation of links between infections and NDDs has been growing.

從那時起，感染與 NDD 之間的聯繫就越來越多。

It seems like when a severe infection happens, an NDD becomes more likely to follow.

似乎一旦發生嚴重感染，NDD 就更有可能接踵而至。

But those links are both really hard to pin down and hotly debated.

但這些聯繫都很難確定，而且爭論激烈。

Here's how we're connecting the dots and maybe, just maybe, kicking some of our most devastating diseases to the curb.

以下是我們如何將這些點聯繫起來，也許，僅僅是也許，就能將一些最具破壞性的疾病消滅在萌芽狀態。

INTRO

導言

Establishing for sure that the flu or mono causes Alzheimer's is super ridiculously difficult.

要確定流感或單核細胞增多症會導致老年痴呆症，難度可想而知。

Like I said, the flu virus causes the flu, the monovirus causes mono, and the shingles virus causes shingles.

就像我說的，流感病毒導致流感，單核病毒導致單核，帶狀皰疹病毒導致帶狀皰疹。

Well, and chickenpox.

嗯，還有水痘。

So saying they also cause Alzheimer's might seem like a totally wild take.

是以，說它們也會導致阿爾茨海默氏症似乎完全是天方夜譚。

We'll get to how it might happen in a little bit, but the main thing epidemiologists want to see is, does X cause Y?

我們稍後會討論它是如何發生的，但流行病學家主要想知道的是，X 是否會導致 Y？

They can worry about the how once they know the what.

一旦他們知道了 "是什麼"，就可以擔心 "怎麼做 "了。

And yes, viral infections might cause NDDs.

是的，病毒感染可能會導致 NDD。

At least, an association between the two is starting to show up everywhere you look.

至少，這兩者之間的聯繫開始隨處可見。

So far, the links are still fuzzy, but there are very specific elements researchers know to look for in order to prove that a specific factor causes a specific disease.

到目前為止，這些聯繫還很模糊，但研究人員知道，要證明某種特定因素導致某種特定疾病，需要尋找一些非常具體的因素。

The first thing you have to do is nail down the timeline.

首先要確定時間表。

It seems obvious, but historically, one of the most important and challenging parts of figuring out whether infections cause NDDs has been establishing that people had the viruses first.

這似乎是顯而易見的，但從歷史上看，要弄清感染是否會導致 NDDs，最重要和最具挑戰性的部分之一就是首先確定人們感染了病毒。

Because we can't say viruses are causing NDDs if the patient's already had Alzheimer's before they got infected.

因為如果患者在感染前就已經患有阿爾茨海默氏症，我們就不能說是病毒導致了 NDDs。

That isn't how time works.

時間不是這樣運作的。

Luckily, figuring this out got a whole lot easier with the rise of electronic health records.

幸運的是，隨著電子病歷的興起，弄清楚這些問題變得容易多了。

In 2023, a study published in the journal Cell analyzed health records from over 300,000 people thanks to a massive database in Finland.

2023年，發表在《細胞》雜誌上的一項研究分析了30多萬人的健康記錄，這要歸功於芬蘭的一個大型數據庫。

That is a lot of people.

那就是很多人。

They identified patients with a bunch of different NDDs, Alzheimer's, dementia, Parkinson's,

他們發現了許多不同的 NDDs 患者，包括阿爾茨海默氏症、痴呆症和帕金森氏症、

ALS, and so on.

ALS 等。

Then the researchers looked up to 15 years back in their record for any severe viral infections.

然後，研究人員查閱了他們長達 15 年的嚴重病毒感染記錄。

We're talking flu, mono, pneumonia, herpes, stomach viruses, shingles, and more.

我們說的是流感、單核細胞增多症、肺炎、皰疹、胃部病毒、帶狀皰疹等等。

Then they compared that group to people who also had an infection but were never diagnosed with an NDD.

然後，他們將這一組人與同樣受到感染但從未被診斷出患有 NDD 的人進行了比較。

The results were striking.

結果令人震驚。

They found 45 viral exposures, which significantly increased risk for developing an NDD in the future.

他們發現，45 種病毒暴露會顯著增加未來患上 NDD 的風險。

And that's interesting.

這很有趣。

But if the research team stopped there, their results probably wouldn't be super trustworthy.

但是，如果研究小組就此止步，他們的研究結果可能就不太可信了。

See, both these infections, like flu and many NDDs, like Alzheimer's, are all really common.

你看，無論是流感等感染性疾病，還是阿爾茨海默氏症等許多非傳染性疾病，都非常常見。

And when you take a bunch of really common things and do some statistics at them, the math is sometimes going to come up as a match by pure random chance.

而當你把一堆非常普通的東西進行統計時，數學上有時會出現純屬偶然的匹配。

A tiny bit like those infinite monkeys coming up with the text of Hamlet, it'll happen eventually.

就像那些無窮無盡的猴子想出《哈姆雷特》的文本一樣，終究會實現的。

In statistics, this practice is called phishing because you're casting a really wide net to fish for significant results.

在統計學中，這種做法被稱為網絡釣魚，因為你是在廣撒網，撈取重大成果。

That means some of those 45 associations were probably not actually real.

這意味著，這 45 個關聯中的一些可能並不真實。

So the team turned to a different, huge database of health records, this one from the UK.

於是，研究小組轉向另一個龐大的健康記錄數據庫，這個數據庫來自英國。

They successfully reproduced 22 of the original 45 associations from that dataset, suggesting there might well be something to them.

他們成功地再現了該數據集中最初 45 種關聯中的 22 種，這表明這些關聯可能是有道理的。

The strongest association was between viral encephalitis, a virus causing inflammation in the brain, and Alzheimer's.

病毒性腦炎（一種導致腦部發炎的病毒）與阿爾茨海默氏症之間的聯繫最為密切。

It showed that being hospitalized with encephalitis increased someone's risk for developing Alzheimer's by 22 to 30 times.

研究表明，因腦炎住院的人患阿爾茨海默氏症的風險會增加 22 到 30 倍。

Reproducing their findings with data from a different country is a great start.

用不同國家的數據複製他們的研究結果是一個很好的開始。

But what is maybe even more persuasive is the number of other researchers that have independently come to the same conclusion about viruses and NDDs.

但更有說服力的是，許多其他研究人員也獨立得出了關於病毒和 NDD 的相同結論。

Researchers have found similar links between mono and multiple sclerosis, mono and Alzheimer's, and flu and Parkinson's.

研究人員發現，單核細胞增多症與多發性硬化症、單核細胞增多症與阿爾茨海默氏症、流感與帕金森氏症之間也存在類似的聯繫。

So the evidence is building for links between viruses and neurodegeneration, but that's still not rock-solid proof that viruses are causing neurodegeneration.

是以，病毒與神經退行性病變之間聯繫的證據正在不斷增加，但這仍不是病毒導致神經退行性病變的確鑿證據。

It's just that this connection is really hard to study.

只是這種聯繫真的很難研究。

If these NDDs pop up between 1 and 15 years after the infection, that's a long time to keep track of hundreds of thousands of people.

如果這些 NDD 在感染後 1 到 15 年間出現，那麼要追蹤數十萬人的情況，時間可就太長了。

The gold standard of proof would be some kind of clinical trial where we'd find people, infect them with a virus, and then watch them in a controlled environment to see if they develop Parkinson's or something.

證明的黃金標準是某種臨床試驗，我們找到一些人，用病毒感染他們，然後在受控環境中觀察他們是否患上帕金森症或其他疾病。

And while a study like that has actually been done successfully in rats, you cannot do that to people and should not try.

雖然這樣的研究在老鼠身上取得了成功，但你不能對人這樣做，也不應該嘗試。

So public health researchers instead use real-world data to make observations.

是以，公共衛生研究人員轉而使用真實世界的數據進行觀察。

For instance, several studies have shown that getting vaccinated for the flu, shingles, and pneumonia can reduce the risk of developing Alzheimer's and Parkinson's.

例如，多項研究表明，接種流感、帶狀皰疹和肺炎疫苗可以降低患老年痴呆症和帕金森症的風險。

That tells us a few important things.

這告訴我們一些重要的事情。

First, while vaccines don't prevent all cases of infection, they can dramatically reduce the severity of those infections.

首先，雖然疫苗不能預防所有的感染病例，但它們可以大大降低感染的嚴重程度。

And that's important because that big study we were talking about earlier with hundreds of thousands of people, that was looking at hospital data.

這一點很重要，因為我們之前提到的那項涉及數十萬人的大型研究，研究對象是醫院數據。

And since you usually don't check into the hospital when you have the flu, that means we're talking about severe infections.

由於患流感時通常不會去醫院，這意味著我們談論的是嚴重感染。

Vaccines are available for several of the viruses they looked at, including flu, shingles, and pneumonia, and they've all been shown to reduce infection severity or rates of hospitalization.

在他們研究的幾種病毒中，包括流感、帶狀皰疹和肺炎，都有疫苗可供選擇，而且這些疫苗都被證明可以降低感染的嚴重程度或住院率。

So it could be getting severe infections leads to higher odds of developing an NDD later in life.

是以，嚴重感染可能會導致日後患上 NDD 的機率增高。

It also means we may be able to prevent people from developing NDDs with a few safe routine shots.

這也意味著，我們或許可以通過一些安全的常規注射預防人們患上 NDD。

So the question remains, if viruses cause NDDs, why and how do they do that?

那麼問題來了，如果病毒會導致 NDD，它們為什麼會這樣做，又是如何做到的呢？

Why would a stomach virus so nasty you end up in the hospital cause problems for your brain?

為什麼噁心得要進醫院的胃病毒會對大腦造成影響？

And not right away, but 15 years later?

不是馬上，而是 15 年之後？

Having a plausible explanation is not strictly necessary for establishing that viruses cause

嚴格來說，要確定病毒會導致以下後果，並非必須要有合理的解釋

NDDs, but it does make researchers' jobs easier when you get to the prevention part.

NDDs，但當你進入預防環節時，它確實會讓研究人員的工作變得更輕鬆。

So to start off, it's not unheard of for viruses to cause a chronic, non-infectious disease.

是以，首先，病毒導致慢性非傳染性疾病的情況並非聞所未聞。

Human papillomavirus, also called HPV, is well known to cause cervical cancer, for example.

例如，眾所周知，人乳頭瘤病毒（又稱 HPV）可導致宮頸癌。

But we're looking at a bunch of different viruses, flu, shingles, mono, herpes, leading to a bunch of similar NDDs.

但我們現在看到的是一系列不同的病毒，流感、帶狀皰疹、單核細胞增多症、皰疹，導致了一系列類似的 NDDs。

It's weird that they seem to end up in the same place.

奇怪的是，它們似乎最終會出現在同一個地方。

It could happen a bunch of ways and might be different for each virus, but here are two of the explanations researchers have put forward.

發生這種情況的方式有很多種，每種病毒的情況也可能不同，但以下是研究人員提出的兩種解釋。

First, remember that all NDDs are caused by a buildup of protein gunk in our nervous system.

首先，請記住，所有 NDD 都是由神經系統中的蛋白質垃圾堆積引起的。

And second, all of these viruses can be neurotropic, meaning they can enter and infect cells in our brain and nervous system.

其次，所有這些病毒都具有神經毒性，這意味著它們可以進入並感染我們大腦和神經系統中的細胞。

Of particular note is herpes, or HSV-1.

特別值得注意的是皰疹，即 HSV-1。

Over 60% of the adult population in the US is estimated to have herpes.

據估計，美國有超過 60% 的成年人患有皰疹。

Most of the time you hear about herpes, it's because of the painful sores it can periodically cause on people's lips and eyes.

你聽到皰疹的大部分原因是它會定期在人們的嘴脣和眼睛上造成疼痛的潰瘍。

In between flare-ups, the herpes virus lays dormant in our peripheral nervous system.

在皰疹發作的間歇期，皰疹病毒會潛伏在我們的周圍神經系統中。

Tons of things, from stress to sunlight and even other infections, can reactivate the producing more baby viruses that travel down to the skin and cause sores again.

從壓力到陽光，甚至是其他感染，有很多東西都會重新激活產生更多的嬰兒病毒，這些病毒會下行到皮膚，再次引起潰瘍。

But those new viruses can also migrate the other direction, from the nerves in our skin up to the brain.

但是，這些新病毒也可以向另一個方向遷移，從我們皮膚上的神經直達大腦。

HSV-1 infections in the brain are usually completely asymptomatic, but even mild brain infections can be harmful, and HSV-1 seems to linger forever.

腦部感染 HSV-1 通常完全沒有症狀，但即使是輕微的腦部感染也會對人體造成危害，而且 HSV-1 似乎會永遠存在。

And in mice, anytime those dormant viruses reactivate, they for some reason ramp up production of the same toxic proteins that make up the plaques in Alzheimer's patients, essentially accelerating neurodegeneration.

而在小鼠體內，只要這些休眠病毒重新激活，它們就會出於某種原因加速產生與阿爾茨海默氏症患者斑塊相同的有毒蛋白質，從根本上加速神經變性。

Since both herpes and all those other viruses are common, severe bouts with the flu or shingles may be repeatedly triggering mild herpes infections in the brain, which could help explain why

由於皰疹和所有其他病毒都很常見，嚴重的流感或帶狀皰疹可能會反覆引發大腦中的輕度皰疹感染，這可以幫助解釋為什麼

NDDs are correlated with so many different viruses.

NDD 與許多不同的病毒都有關聯。

So it's all herpes' fault.

所以這都是皰疹的錯。

Maybe.

也許吧

Another proposed mechanism has to do with the molecular cause of NDDs.

另一種建議的機制與 NDD 的分子原因有關。

One thing viruses and NDDs have in common is that they both make big protein complexes in our cells.

病毒和 NDD 的一個共同點是，它們都會在我們的細胞中製造大型蛋白質複合物。

For viruses, those complexes are new baby viruses, but in NDDs, they're globs of smaller proteins all stuck together in our nervous system.

對於病毒來說，這些複合物是新生的病毒，但對於 NDD 而言，它們是神經系統中粘在一起的小蛋白質球。

For viruses to replicate, they need to hijack our cellular machinery to assemble new viruses.

病毒要進行復制，就需要劫持我們的細胞機器來組裝新病毒。

But it's possible the changes they make to our cellular machinery could linker even after the viruses stop replicating.

但是，病毒對我們細胞機制的改變有可能在病毒停止複製後仍會繼續存在。

The faulty cellular machinery could, you might say, get confused.

你可能會說，有問題的細胞機器可能會感到困惑。

It's now programmed to assemble proteins into new viruses, but it's all out of virus.

它現在的程序是將蛋白質組裝成新的病毒，但它已經沒有病毒了。

Instead, they might accidentally start globbing human proteins together, improperly creating those harmful plaques that cause NDDs.

相反，它們可能會意外地將人體蛋白質凝結在一起，不恰當地形成導致 NDD 的有害斑塊。

One study, which hasn't been through the peer review process yet as we are filming this, does present some early evidence supporting this idea.

在我們拍攝這篇文章時，有一項研究還沒有通過同行評審，但它確實提出了一些支持這一觀點的早期證據。

The study shows that a drug that was originally designed to interrupt the assembly of HIV viruses can also slow the assembly of plaques in patients with ALS.

這項研究表明，一種原本用於阻斷艾滋病病毒組裝的藥物也能減緩漸凍症患者體內斑塊的組裝。

So maybe those plaques are being put together in a similar way, and the drug is resetting the faulty machinery.

是以，也許這些斑塊是以類似的方式拼湊在一起的，而藥物正在重置有問題的機器。

These ideas require further study, but they lend some weight to the notion that viruses are causing NDDs.

這些觀點還需要進一步研究，但它們為病毒導致 NDD 的說法提供了一些依據。

All in all, while it's still up in the air, the growing body of research certainly checks a lot of the boxes epidemiologists look for when declaring a causative relationship.

總之，雖然目前還沒有定論，但越來越多的研究肯定符合流行病學家在宣佈因果關係時所尋找的許多條件。

And we might get clarity on this relationship in the coming years.

在未來的幾年裡，我們可能會弄清這種關係。

The world is reeling from the COVID-19 pandemic caused by SARS-CoV-2, a virus that can infect the brain.

由 SARS-CoV-2 病毒引發的 COVID-19 大流行正在席捲全球，SARS-CoV-2 是一種可感染大腦的病毒。

And if severe viral infections really do cause NDDs, then we would expect to see an uptick in Alzheimer's and Parkinson's over the next 10-15 years.

如果嚴重的病毒感染真的會導致 NDDs，那麼在未來 10-15 年內，我們有望看到阿爾茨海默氏症和帕金森氏症的發病率上升。

Some papers suggest it's already happening, but like all science, we need to wait for many researchers to come to that same conclusion before we can make that call.

一些論文表明，這種情況已經發生，但就像所有科學一樣，我們需要等待許多研究人員得出同樣的結論後才能做出判斷。

Time will tell.

時間會證明一切。

Now maybe this seems like terrible news.

現在看來，這也許是個可怕的消息。

We all get the flu, we all get mono, and we all get herpes.

我們都會得流感，都會得單核細胞增多症，都會得皰疹。

So how does knowing they might be causing NDDs make any difference?

那麼，知道它們可能導致 NDD 又有什麼區別呢？

Because knowing that viruses may be partially causing some of the most devastating diseases humans experience empowers us to find solutions.

因為知道病毒可能是導致人類經歷的一些最具破壞性疾病的部分原因後，我們就有能力找到解決方案。

We've learned that vaccines for common viruses seem to protect us from NDDs.

我們已經瞭解到，普通病毒疫苗似乎可以保護我們免受非傳染性疾病的侵襲。

Those vaccines prevent severe infections, and severity appears to be a factor.

這些疫苗可以預防嚴重感染，而嚴重程度似乎是一個因素。

There are also other ways to reduce the severity of some infections, like Tamiflu for flu, or Paxlovid for COVID-19.

也有其他方法可以減輕某些感染的嚴重程度，如治療流感的特敏福或治療 COVID-19 的 Paxlovid。

And while not all of these viruses have vaccines yet, they're working on it.

雖然這些病毒還沒有全部都有疫苗，但他們正在努力研究。

For all of history, Alzheimer's, Parkinson's, and dementia have felt like almost unavoidable problems we have to accept as we age.

從古至今，阿爾茨海默氏症、帕金森氏症和痴呆症幾乎都是我們隨著年齡增長而不得不接受的問題。

What if that's not the case?

如果情況並非如此呢？

What if these heartbreaking diseases have such easy-to-tackle causes that we could be on the verge of getting rid of them?

如果這些令人心碎的疾病的病因如此容易解決，以至於我們即將擺脫它們，那該怎麼辦？

At least some of them.

至少是一部分。

It's not going to happen next year, or in five years.

這不會在明年或五年內發生。

But if these associations with infections turn out to be real, we suddenly have a massive toolkit for dealing with neurodegenerative diseases.

但是，如果這些與感染的關聯被證實是真實的，那麼我們就突然擁有了一個處理神經退行性疾病的龐大工具包。

Vaccines and treatments that we already know are safe and effective.

我們已經知道安全有效的疫苗和治療方法。

C'mon science, give us this one!

來吧，科學，給我們這個！

[♪ OUTRO ♪, thanks for watching!]

[OUTRO，感謝您的收看！]