Paul Ewald: Can we domesticate germs?

譯者: Inder Peng(彭) 審譯者: Shelley Krishna Tsang

What I'd like to do is just drag us all down into the gutter,

我想要做的就是把大家都拖到排水溝裡，

and actually all the way down into the sewer

其實是一路滑下到下水道，

because I want to talk about diarrhea.

因為我想談的是有關於腹瀉。

And in particular, I want to talk about

更具體而言,我想談談

the design of diarrhea.

腹瀉的設計圖譜

And when evolutionary biologists talk about design,

當生物進化學家們談論設計時

they really mean design by natural selection.

真正指的是經由自然選擇的設計，

And that brings me to the title of the talk,

這也就是我的演講標題

"Using Evolution to Design Disease Organisms Intelligently."

“聰明巧妙的使用生物進化去設計病菌."

And I also have a little bit of a sort of smartass subtitle to this.

我也有加上有一點自負的副標題,

But I'm not just doing this to be cute.

但這樣做不是要譁眾取寵.

I really think that this subtitle explains

我真的認為這副標題幫這些像我一樣

what somebody like me, who's sort of a Darwin wannabe,

想要成為達爾文第二的人闡述了心聲

how they actually look at one's role in

表達他們是如何真正看待自己

sort of coming into this field of health sciences and medicine.

在健康科學和醫學領域裡的角色。

It's really not a very friendly field for evolutionary biologists.

對進化生物學家來說這實在不是一個很友好的領域。

You actually see a great potential,

雖然具有強大潛力，

but you see a lot of people who are sort of defending their turf,

但你也會看到很多人固步自封，

and may actually be very resistant, when one tries

有時當試圖引進這些想法時

to introduce ideas.

會被強烈排斥。

So, all of the talk today is going to deal with two general questions.

今天演講的主題是要針對兩個很普通的問題.

One is that, why are some disease organisms more harmful?

一個是，為什麼有些病菌比較有殺傷力

And a very closely related question, which is,

而一個非常密切相關的問題是:

how can we take control of this situation once we understand

一旦我們知道第一個問題的答案後,

the answer to the first question?

我們如何才能控制這種情況？

How can we make the harmful organisms more mild?

如何使殺傷力強的病菌變成比較溫和呢？

And I'm going to be talking, to begin with, as I said,

而我將討論的,正如我所說，

about diarrheal disease organisms.

首先關於腹瀉疾病的病菌。

And the focus when I'm talking about the diarrheal organisms,

我的焦點不僅僅是討論各種腹瀉的病菌

as well as the focus when I'm talking about any organisms

而且還包括當談論任何病菌

that cause acute infectious disease,

造成急性傳染病時

is to think about the problem from a germ's point of view,

用病菌的角度來思考問題.

germ's-eye view.

病菌的觀點.

And in particular, to think about a fundamental idea

用這方法來思考探究一個根本的想法,

which I think makes sense out of a tremendous amount of variation

我覺得很合理, 尤其是面對殺傷力強

in the harmfulness of disease organisms.

且具有大量變異性的病源體時.

And that idea is that from the germ's-eye point of view,

從細菌的角度來看世界,

disease organisms have to get from one host to another,

通常病菌必須從一個宿主轉移到另一個宿主,

and often they have to rely on the well-being of the host

他們往往必需要依靠還算健康的宿主

to move them to another host.

來傳染疾病到另一個宿主.

But not always.

但並非總是如此。

Sometimes, you get disease organisms

有時候,讓人得到疾病的病源體

that don't rely on host mobility at all for transmission.

不依賴宿主的活動力來傳播疾病。

And when you have that, then evolutionary theory tells us

這情形下,進化理論告訴我們，

that natural selection will favor the more exploitative,

自然選擇將有利於比較兇猛，

more predator-like organisms.

更具侵略性的病源體，

So, natural selection will favor organisms

也就是自然選擇將有利

that are more likely to cause damage.

於殺傷力強的病源體，

If instead transmission to another host requires host mobility,

相反的,如果需要依賴宿主的活動性來傳播疾病,

then we expect that the winners of the competition

我們可以預料競爭中的贏家

will be the milder organisms.

將是溫和的菌種.

So, if the pathogen doesn't need the host to be healthy and active,

所以,如果病源體不需要健康活動的宿主來傳播疾病,

and actual selection favors pathogens

那實際上自然選擇的病源體,

that take advantage of those hosts,

是有利於會佔盡宿主的便宜,摧殘宿主的菌種,

the winners in the competition are those that exploit the hosts

所以競爭中的贏家是那些剝削宿主

for their own reproductive success.

來繁殖自己的病源體.

But if the host needs to be mobile in order to transmit the pathogen,

但是,如果需要宿主的活動力來傳播疾病

then it's the benign ones that tend to be the winners.

那麼那些較溫和的病源體,往往會成為贏家.

So, I'm going to begin by applying this idea to diarrheal diseases.

所以我將開始應用這一想法到腹瀉的疾病上。

Diarrheal disease organisms get transmitted in basically three ways.

腹瀉的病菌基本是以三種方式傳播。

They can be transmitted from person-to-person contact,

它們可以由人接觸傳染到另一人，

person-to-food-then-to-person contact,

(人-食物-人)

when somebody eats contaminated food,

人吃下被污染的食物而傳染

or they can be transmitted through the water.

或者通過水傳播。(水媒)

And when they're transmitted through the water,

如果通過水傳播，

unlike the first two modes of transmission,

那就不像前兩種模式傳染，

these pathogens don't rely on a healthy host for transmission.

這些病源體不依賴於一個健康的宿主傳播病源體。

A person can be sick in bed and still infect tens, even hundreds

一個人可以是重病在床,仍然感染其他人，

of other individuals.

甚至數百個人。

To sort of illustrate that, this diagram emphasizes that

這附圖可說明更清楚,這圖強調，

if you've got a sick person in bed,

如果有一個生病的人在床上，

somebody's going to be taking out the contaminated materials.

有人需要處理被污染的器皿,

They're going to wash those contaminated materials,

他們將清洗這些受污染的器具.

and then the water may move into sources of drinking water.

然後髒水可能進入飲用水源中,

People will come in to those places where you've got

人們會去在那些地方取水,

contaminated drinking water,

而這些是被污染的飲用水.

bring things back to the family,

他們會把水帶回家,

may drink right at that point.

有時就在水源處喝上幾口.

The whole point is that a person who can't move

整個的重點是:一個人即使沒有活動力

can still infect many other individuals.

仍然可以感染許多其他個人。

And so, the theory tells us that

所以,理論告訴我們，

when diarrheal disease organisms are transported by water,

當腹瀉的病菌是經由水傳播，

we expect them to be more predator-like, more harmful.

我們可預料病源體更凶狠,更有害的。

And you can test these ideas.

而且,您可以測試這些推論。

So, one way you can test is just look at all diarrheal bacteria,

只需看看所有腹瀉細菌們，

and see whether or not the ones that tend to be

看是否那些更趨向於利用水傳播

more transmitted by water, tend to be more harmful.

的病源體,往往更有殺傷力?

And the answer is -- yep, they are.

答案是-沒錯，它們是。

Now I put those names in there just for the bacteria buffs,

現在我為細菌迷把很多病菌名字列在此，

but the main point here is that --

但主要的一點是 -

(Laughter)

（眾笑）

there's a lot of them here, I can tell --

我敢說,這裡很多是細菌迷-

the main point here is that those data points

重點是，這些數據點

all show a very strong, positive association between

均表現出非常強烈的正向關聯:

the degree to which a disease organism is transmitted by water,

越是依賴水傳播疾病的病菌,

and how harmful they are,

殺傷力越強.

how much death they cause per untreated infection.

以及如果未經治療的死亡率.

So this suggests we're on the right track.

因此,這表示我們的推論是正確的,

But this, to me, suggests that we really need

我建議我們真的需要

to ask some additional questions.

深入探討這現象.

Remember the second question that I raised at the outset was,

記得我在一開始就提出了的第2個問題嗎:

how can we use this knowledge

我們如何用這些知識，

to make disease organisms evolve to be mild?

使病源體進化成較溫和的細菌呢？

Now, this suggests that if you could just block waterborne transmission,

所以現在假設如果你能阻止水媒傳播,

you could cause disease organisms to shift from

那表明就能把這種細菌們的

the right-hand side of that graph to the left-hand side of the graph.

進化從圖中的右邊推向到左邊去.

But it doesn't tell you how long.

但是我們不知要多久,進化才能完成.

I mean, if this would require thousands of years,

我的意思是,如果這將需要數千年,

then it's worthless in terms of controlling of these pathogens.

那不值得去試控制這些病源體。

But if it could occur in just a few years,

但如果它可能發生在短短幾年內,

then it might be a very important way to control

那麼它可能是一個非常重要的方式,來控制

some of the nasty problems that we haven't been able to control.

那些我們以前沒法控制,難纏困難的問題.

In other words, this suggests that we could

換言之,這表明我們可以

domesticate these organisms.

馴養這些細菌們,

We could make them evolve to be not so harmful to us.

使他們進化成較溫和的細菌.

And so, as I was thinking about this, I focused on this organism,

所以,當我在作研究時我把重心放在這個EL Tor(埃爾托)

which is the El Tor biotype of the organism called Vibrio cholerae.

生物型的細菌上,也就是被稱為霍亂弧菌的菌種.

And that is the species of organism that is responsible

這種病源體是造成

for causing cholera.

霍亂的原因。

And the reason I thought this is a really great organism to look at

而我之所以認為研究這菌種是很棒的題材,

is that we understand why it's so harmful.

是因為我們已知道它為什麼如此有殺傷力。

It's harmful because it produces a toxin,

它的有害,是因為它會產生一種毒素.

and that toxin is released when the organism

當霍亂弧菌進入我們的腸道的時候,

gets into our intestinal tract.

毒素會被釋放出來.

It causes fluid to flow from the cells that line our intestine

這會使體液從腸壁細胞流入腸道(腔)中

into the lumen, the internal chamber of our intestine,

--就是腸子中間的內在管腔.

and then that fluid goes the only way it can, which is out the other end.

然後，這液體流向唯一可去的另一端,排出人體外.

And it flushes out thousands of different other competitors

經由這過程沖刷走數以千計不同種腸道內競爭菌種,

that would otherwise make life difficult for the Vibrios.

使霍亂弧菌可以容易生存繁殖下來.

So what happens, if you've got an organism,

然後呢?如果有一種病源體在體內,

it produces a lot of toxin.

它產生大量的毒素.

After a few days of infection you end up having --

經過幾天後最終的結果是--

the fecal material really isn't so disgusting as we might imagine.

糞便排洩物並不像我們想的那麼噁心.

It's sort of cloudy water.

只是一灘混濁的水.

And if you took a drop of that water,

如果你從中取一滴的水,

you might find a million diarrheal organisms.

你會發現一百萬腹瀉病源體在其中.

If the organism produced a lot of toxin,

如果病源體產生了大量的毒素,

you might find 10 million, or 100 million.

你可能會找到1千萬或1億個病源體.

If it didn't produce a lot of this toxin,

但如果病源體沒有產生了大量的毒素,

then you might find a smaller number.

可能只會被發現較少量的病源體.

So the task is to try to figure out

因此,主要的任務是設法弄清楚

how to determine whether or not you could get an organism like this

如何能確定是否經由阻斷它們的水媒介傳播途徑,

to evolve towards mildness by blocking waterborne transmission,

可以使這種殺傷力強的病源體進化成較溫和的病源體

thereby allowing the organism only to be transmitted

從而使傳播途徑只有

by person-to-person contact,

人對人直接接觸,

or person-food-person contact --

或人-食物-人的接觸感染.

both of which would really require that people be

而此二種都是需要有

mobile and fairly healthy for transmission.

足夠活動力或還算健康的人來傳播.

Now, I can think of some possible experiments.

於是,我能想到一些可能的實驗。

One would be to take a lot of different strains of this organism --

其中之一是採取了很多同種病菌的不同菌株(不同亞型)

some that produce a lot of toxins, some that produce a little --

一些會產生大量的毒素，一些只產生少數的毒素-

and take those strains and spew them out in different countries.

把這些不同菌株，散播在不同的國家。

Some countries that might have clean water supplies,

有些國家有清潔食水供應

so that you can't get waterborne transmission:

所以不能利用水來傳播，

you expect the organism to evolve to mildness there.

您可以預期在那裡病菌的進化會更溫和。

Other countries, in which you've got a lot of waterborne transmission,

但有些國家,有很多水媒傳播機會，

there you expect these organisms to evolve

所以你預期這些病菌的生物進化,

towards a high level of harmfulness, right?

會邁向更有殺傷力的方向,對不對？

There's a little ethical problem in this experiment.

這實驗會面臨一個道德問題。

I was hoping to hear a few gasps at least.

我以為會聽到一些人(驚嚇的)倒抽一口氣。

That makes me worry a little bit.

這就會使我有點擔心。

(Laughter)

笑聲

But anyhow, the laughter makes me feel a little bit better.

不過,無論如何,笑聲讓我覺得好一點。

And this ethical problem's a big problem.

而這種道德問題是一個大問題。

Just to emphasize this, this is what we're really talking about.

為了強調這一點,也這就是我們真正談論的。

Here's a girl who's almost dead.

看這女孩差一點死了。

She got rehydration therapy, she perked up,

她得到了支持性補充體液療法,才恢復起來，

within a few days she was looking like a completely different person.

幾天之內,她看上去像一個完全不同的人。

So, we don't want to run an experiment like that.

因此,我們不希望進行這樣的實驗。

But interestingly, just that thing happened in 1991.

但有意思的是,類似的狀況發生在1991年。

In 1991, this cholera organism got into Lima, Peru,

1991年,霍亂病菌侵襲秘魯首都利馬，

and within two months it had spread to the neighboring areas.

並在兩個月內,蔓延到鄰近地區(國家)。

Now, I don't know how that happened,

即使是現在我也不知道為什麼發生那瘟疫，

and I didn't have anything to do with it, I promise you.

我向你們保證,那跟我沒有任何關係。

I don't think anybody knows,

我不認為有人知道為什麼會發生，

but I'm not averse to, once that's happened,

一旦這發生了,我不反對，

to see whether or not the prediction that we would make,

借由這機會來分析看看是否我們的推論是對的，

that I did make before, actually holds up.

就是我曾經提出過的理論,是否經得起考驗。

Did the organism evolve to mildness in a place like Chile,

在智利是否霍亂病菌進化成較溫和的菌種,

which has some of the most well protected water supplies

因為智利在拉丁美洲具有最為完善的

in Latin America?

水源保護系統?

And did it evolve to be more harmful in a place like Ecuador,

是否在厄瓜多爾霍亂病菌進化成殺傷力更強的菌種

which has some of the least well protected?

因為厄瓜多爾的水源最不受保護?

And Peru's got something sort of in between.

而秘魯對水源的保護程度是介在兩國之間.

And so, with funding from the Bosack-Kruger Foundation,

因為有Bozack-Kruger基金會的財政協助,

I got a lot of strains from these different countries

我們從這些國家得到了很多不同的菌株.(樣品)

and we measured their toxin production in the lab.

我們於是在實驗室測量它們產生的毒素.

And we found that in Chile -- within two months of the invasion of Peru

我們發現,在智利-霍亂入侵秘魯兩個月後,

you had strains entering Chile --

霍亂病菌漫延入智利.

and when you look at those strains,

仔細研究這些菌株(種),

in the very far left-hand side of this graph,

在這個圖的最左邊,

you see a lot of variation in the toxin production.

毒素的生產量有很大的變異性(很多不同的菌株)

Each dot corresponds to an islet from a different person --

每個點或一個島形代表來自不同的個人

a lot of variation on which natural selection can act.

自然選擇可以倒導致很多變化.

But the interesting point is, if you look over the 1990s,

但有趣的一點是,如果你看整個1990年代,

within a few years the organisms evolved to be more mild.

在幾年內霍亂病菌進化成較溫和的菌種.

They evolved to produce less toxin.

它們發展成只會產生少量毒素的菌種.

And to just give you a sense of how important this might be,

更清楚的讓你們瞭解這個的重要性,

if we look in 1995, we find that there's only one case of cholera,

如果研究1995年只有一個霍亂病例,

on average, reported from Chile every two years.

平均每二年只有一個霍亂病例.

So, it's controlled.

所以,霍亂被控制住了.

That's how much we have in America,

這跟在美國發生律一樣.

cholera that's acquired endemically,

霍亂是一種區域性的瘟疫.

and we don't think we've got a problem here.

我不認為在美國我們有霍亂瘟疫的問題.

They didn't -- they solved the problem in Chile.

它們不是問題--在智利他們解決了這個瘟疫問題.

But, before we get too confident, we'd better look at some of those other countries,

但在我們過於自信前,我們最好看看其他的鄰近國家.

and make sure that this organism doesn't just always evolve toward mildness.

並確認這些病菌(不是)只朝著更溫和的方向進化.

Well, in Peru it didn't.

嗯,在秘魯病菌就不是變溫和。

And in Ecuador -- remember, this is the place where it has

而在厄瓜多爾-記得嗎這地方的

the highest potential waterborne transmission --

水媒傳輸可能性最高-

it looked like it got more harmful.

-看起來病菌進化得更有殺傷力.

In every case there's a lot of variation,

每個例子都有很多變異性,

but something about the environment the people are living in,

這是與人們居住的環境有關.

and I think the only realistic explanation is that it's

我認為唯一真正的解釋是在於

the degree of waterborne transmission,

病菌水媒傳輸的程度.

favored the harmful strains in one place, and mild strains in another.

所以有些地區進化成殺傷力強的菌種.有些則進化成溫和菌種.

So, this is very encouraging,

因此,這結果非常令人興奮，

it suggests that something that we might want to do anyhow,

這代表有些事我們應該去做,

if we had enough money, could actually give us a much bigger bang for the buck.

如果我們有足夠的錢，我們可更有效率的利用這錢來(控制瘟疫)

It would make these organisms evolve to mildness,

使這些病菌進化成溫和菌種.

so that even though people might be getting infected,

所以,即使人們可能被感染，

they'd be infected with mild strains.

他們只會被溫和的菌種(株)感染

It wouldn't be causing severe disease.

不會引起嚴重的症狀.

But there's another really interesting aspect of this,

還有更有意思的另方面是:

and this is that if you could control the evolution of virulence,

如果我們可以控制病毒性的演變，

evolution of harmfulness,

危害性的進化.

then you should be able to control antibiotic resistance.

那我們應該能夠控制抗生素的耐藥性

And the idea is very simple.

原理非常簡單,

If you've got a harmful organism,

如果人們被殺傷力強的菌種感染,

a high proportion of the people are going to be symptomatic,

就會有高比例的人生病(症狀嚴重).

a high proportion of the people are going to be going to get antibiotics.

那大量抗生素將會被使用來控制病情,

You've got a lot of pressure favoring antibiotic resistance,

結果會有利於抗生素耐藥性的產生.

so you get increased virulence leading to

也就是增加導致毒性更強

the evolution of increased antibiotic resistance.

且對抗生素產生耐藥性的細菌增加.

And once you get increased antibiotic resistance,

一旦耐藥性增強,

the antibiotics aren't knocking out the harmful strains anymore.

這種抗生素就不再對這菌種(株)產生作用.

So, you've got a higher level of virulence.

那細菌的毒性會更強.

So, you get this vicious cycle.

最後這是個惡性循環.

The goal is to turn this around.

我們的目標是要扭轉這個局面。

If you could cause an evolutionary decrease in virulence

如果可以通過淨化水源來

by cleaning up the water supply,

進化下降細菌病毒性

you should be able to get an evolutionary decrease

那麼也應該經由此進化減少

in antibiotic resistance.

抗生素的耐藥性.

So, we can go to the same countries and look and see.

因此,讓我們再一次仔細研究這三個相同國家.

Did Chile avoid the problem of antibiotic resistance,

到底智利有沒有避免抗生素產生耐藥性的問題？

whereas did Ecuador actually have the beginnings of the problem?

而相對的厄瓜多爾實際上有沒有發生耐藥性的問題？

If we look in the beginning of the 1990s,

如果我們比較90年代的初期,

we see, again, a lot of variation.

我們會發現到很多變異性，(三個國家結果相似)。

In this case, on the Y-axis, we've just got a measure of antibiotic sensitivity --

在此,Y軸代表病菌對抗生素的敏感性,

and I won't go into that.

我不打算深入探討下去.

But we've got a lot of variation in antibiotic sensitivity in Chile,

在智利,秘魯和厄瓜多爾病菌對抗生素的敏感性(有效性)的差異性變化很大.

Peru and Ecuador, and no trend across the years.

(有些菌種對抗生素很敏感;有些不敏感).我們沒有接下去幾年的記錄數據.

But if we look at the end of the 1990s, just half a decade later,

但是如果我們看看90年代末期,短短五年而已,

we see that in Ecuador they started having a resistance problem.

在厄瓜多爾已經開始有抗藥性的問題。

Antibiotic sensitivity was going down.

抗生素的敏感性一直在下降.

And in Chile, you still had antibiotic sensitivity.

在智利抗生素依然保持其敏感性.

So, it looks like Chile dodged two bullets.

因此，可以說智利躲過兩個難題:

They got the organism to evolve to mildness,

(霍亂)病菌進化成溫和菌種,

and they got no development of antibiotic resistance.

而且他們依然保持抗生素的敏感性.

Now, these ideas should apply across the board,

這種理論應該被大量採用,

as long as you can figure out why some organisms evolved to virulence.

只要我們弄清楚為什麼有些病菌會進化到更具毒性.

And I want to give you just one more example,

我想再給你另一個例子瘧疾.

because we've talked a little bit about malaria.

因為我們已經談了一點有關於瘧疾的疾病。

And the example I want to deal with is,

而有關這例子我想表達的是，

or the idea I want to deal with, the question is,

我的想法是,問題是，

what can we do to try to get the malarial organism to evolve to mildness?

我們該如何做能使瘧疾進化溫和呢？

Now, malaria's transmitted by a mosquito,

瘧疾是由蚊子傳播的，

and normally if you're infected with malaria, and you're feeling sick,

通常狀況下如果感染了瘧疾,人會覺得不舒服虛弱，

it makes it even easier for the mosquito to bite you.

所以更容易被蚊子咬。

And you can show, just by looking at data from literature,

只要看看文獻資料,即可以知道,

that vector-borne diseases are more harmful

需要媒介傳播的疾病比無需媒介傳播

than non-vector-borne diseases.

的疾病更有殺傷力.

But I think there's a really fascinating example

但我認為這是一個非常有趣的例子,

of what one can do experimentally to try to actually demonstrate this.

來實際實驗證明我們的理論.

In the case of waterborne transmission,

在這水媒傳播疾病例子,

we'd like to clean up the water supplies,

我們把水源淨化控制,

see whether or not we can get those organisms to evolve towards mildness.

看看是否能不能讓這些病菌進化成更溫和。

In the case of malaria, what we'd like to do is mosquito-proof houses.

但對瘧疾而言,我們想要做的是建防蚊房.

And the logic's a little more subtle here.

邏輯推理上更微妙.

If you mosquito-proof houses,

如果有人得到瘧疾,就把

when people get sick, they're sitting in bed --

他們擱置在防蚊子的房子裡的床上,

or in mosquito-proof hospitals, they're sitting in a hospital bed --

或防蚊子的醫院床上.

and the mosquitoes can't get to them.

蚊子就無法叮他們了.

So, if you're a harmful variant

因此，如果你是一個殺傷力強的細菌變種,

in a place where you've got mosquito-proof housing, then you're a loser.

卻被防蚊子的房子關起來,沒蚊子,那麼你注定是一個失敗者。

The only pathogens that get transmitted

唯一能傳播的病菌(變種)是那些被感染的人

are the ones that are infecting people that feel healthy enough

還有足夠的活力在外面趴趴走,

to walk outside and get mosquito bites.

然後才有機會被蚊蟲叮咬來傳播病菌.

So, if you were to mosquito proof houses,

因此,如果利用防蚊子的房子,

you should be able to get these organisms to evolve to mildness.

我們應該能夠迫使這瘧疾細菌進化成溫和菌種.

And there's a really wonderful experiment that was done

從以下這個完美實驗的結果顯示出:

that suggests that we really should go ahead and do this.

我們真的應該繼續這樣做。

And that experiment was done in Northern Alabama.

那個實驗是在阿拉巴馬州北部實行.

Just to give you a little perspective on this,

為了給你更具體的認知,

I've given you a star at the intellectual center of the United States,

我在美國的知識中心,肯塔基州的路易斯維爾,

which is right there in Louisville, Kentucky.

畫一個星星"*".

And this really cool experiment was done

在那地區大約200英里以南完成這麼酷的實驗.

about 200 miles south of there, in Northern Alabama,

也就是阿拉巴馬州北部，

by the Tennessee Valley Authority.

由於田納西河流域管理局

They had dammed up the Tennessee River.

在田納西河建水庫,

They'd caused the water to back up,

阻斷了水流.

they needed electric, hydroelectric power.

他們需要電，用水來發電.

And when you get stagnant water, you get mosquitoes.

水庫的積水是死水,所以會滋生蚊子.

They found in the late '30s -- 10 years after they'd made these dams --

這是在1930年代末期-- 即是建水壩後的10年後-

that the people in Northern Alabama were infected with malaria,

在阿拉巴馬北部瘧疾開始傳播.

about a third to half of them were infected with malaria.

大約有三分之一到一半的居民人被感染了瘧疾。

This shows you the positions of some of these dams.

這圖標示這些水壩的位置.

OK, so the Tennessee Valley Authority was in a little bit of a bind.

不錯!那時田納西河流域管理局是面臨一些困境.

There wasn't DDT, there wasn't chloroquines: what do they do?

那時沒有DDT(農業),沒有氯奎因(治瘧疾藥) 那他們能做什麼？

Well, they decided to mosquito proof every house in Northern Alabama.

於是他們決定使北阿拉巴馬州家家戶戶都能防蚊.

So they did. They divided Northern Alabama into 11 zones,

他們就這樣做.把北阿拉巴馬州分11個區，

and within three years, about 100 dollars per house,

並在三年內,每家約只用 100美元，

they mosquito proofed every house.

家家戶戶都有防蚊設備

And these are the data.

這些都是當時的數據證明.

Every row across here represents one of those 11 zones.

豎立的每一行各代表這不同的11區。

And the asterisks represent the time at which

這裡星(*)號代表在何時

the mosquito proofing was complete.

在這些區完成防蚊設備.

And so what you can see is that

你可以看到的是只有

just the mosquito-proofed housing, and nothing else,

家家戶戶完成防蚊設備.沒有別的，

caused the eradication of malaria.

就這樣根除瘧疾。

And this was, incidentally, published in 1949,

整個瘟疫只在1949年最具領導地位的

in the leading textbook of malaria, called "Boyd's Malariology."

教科書"Boyd瘧疾病理學"中,曾被順便一提過.

But almost no malaria experts even know it exists.

幾乎沒有任何瘧疾病理專家知道它的存在過.

This is important,

這一點很重要，

because it tells us that if you have moderate biting densities,

因為它告訴我們如果在中度機率被蚊子叮咬的地區,

you can eradicate malaria by mosquito proofing houses.

只要具備防蚊設備就可以根除瘧疾.

Now, I would suggest that you could do this in a lot of places.

所以現在,我建議這方法可被應用在很多地區.

Like, you know, just as you get into the malaria zone,

比如,大家都知的,一些瘧疾區，

sub-Saharan Africa.

如非洲撒哈拉以南的地區.

But as you move to really intense biting rate areas, like Nigeria,

但是如果到被蚊子叮很高機率的區域,像奈及利亞.

you're certainly not going to eradicate.

這招行不通,瘧疾無法根除.

But that's when you should be favoring evolution towards mildness.

可是經由這樣應能有利於讓病菌進化成溫和菌種.

So to me, it's an experiment that's waiting to happen,

對我來說,我期待它的發生.

and if it confirms the prediction, then

如果結果是如我們所預期的,

we should have a very powerful tool.

那麼我們就應該有一個非常有利的工具(方法)。

In a way, much more powerful than the kind of tools we're looking at,

在某種程度上，這是比我們現在使用的方法更得力.

because most of what's being done today is

因為現在我們所做的大多是

to rely on things like anti-malarial drugs.

依賴抗瘧疾藥物去控制瘧疾.

And we know that, although it's great to make those

.儘管藥物現在很便宜很容易取得,

anti-malarial drugs available at really low cost and high frequency,

被大量使用,

we know that when you make them highly available

但我們都知道當藥物被高頻率使用,

you're going to get resistance to those drugs.

那就更容易產生抗藥性而失效.

And so it's a short-term solution.

所以使用藥物控制(瘟疫)只是暫時的解決方案.

This is a long-term solution.

(進化成溫和菌種)這才是長期一勞永逸的方法.

What I'm suggesting here is that we could get evolution

我的建議是我們可以左右細菌進化

working in the direction we want it to go,

使它們向我們希望的方向前進.

rather than always having to battle evolution as a problem

而不是總是跟細菌進化鬥爭和

that stymies our efforts to control the pathogen,

這阻礙我們控制病源體的努力成效

for example with anti-malarial drugs.

比如說抗瘧疾藥物使細菌進化更毒

So, this table I've given just to emphasize

這個圖表只是要強調，

that I've only talked about two examples.

雖然我只談到兩個例子.

But as I said earlier, this kind of logic applies across the board

但正如我剛才所說,這種邏輯適用於

for infectious diseases, and it ought to.

所有傳染性疾病,而且這是應該要做的.

Because when we're dealing with infectious diseases, we're dealing with living systems.

因為當我們面對處理傳染性疾病時,我們面對的是一個生命系統,

We're dealing with living systems;

當面對的是一個生命系統,時

we're dealing with systems that evolve.

生命系統會進化。

And so if you do something with those systems,

所以如果人為對這系統做些干預,

they're going to evolve one way or another.

它不是進化成溫和,就是成殺傷力更強的.

And all I'm saying is that we need to figure out how they'll evolve,

所有我要強調的是,我們需要弄清楚它們會如何進化,

so that -- we need to adjust our interventions

然後我們可以調整我們的干預措施，

to get the most bang for the intervention buck,

得到最大的利益.

so that we can get these organisms to evolve in the direction we want them to go.

使這些細菌朝我們希望它們進化的方向前去.

So, I don't really have time to talk about those things,

我並沒有時間來更深入談論這些事，

but I did want to put them up there,

我這麼做是希望引起大家的注意力

just to give you a sense that there really are solutions

給你們一些更貼切的感覺,我們確實有辦法.

to controlling the evolution of harmfulness

可以控制我們現在所面臨的

of some of the nasty pathogens that we're confronted with.

一些難纏有害的病菌的進化過程.

And this links up with a lot of the other ideas that have been talked about.

這其實與許多已經講過了其他的想法貫通.

So, for example, earlier today there was discussion of,

舉例來說,今天早些時候有討論過的

how do you really lower sexual transmission of HIV?

如何能真的降低性病愛滋病的傳染？

What this emphasizes is that we need to figure out how it will work.

重點是我們需要弄清楚我們該如何做才會有效.

Will it maybe get lowered if we alter the economy of the area?

是不是改變這地區的經濟狀況就可降低愛滋病的得病率?

It may get lowered if we intervene in ways that

如果經由鼓勵人們對性伴侶的

encourage people to stay more faithful to partners, and so on.

忠誠度是否得病率會降低?等等方法.

But the key thing is to figure out how to lower it,

但最主要的關鍵是要弄清楚如何降低愛滋病的傳染率,

because if we lower it, we'll get an evolutionary change in the virus.

因為如果我們能降低傳染率,我們可以促使病毒進化改變.

And the data really do support this:

數據確實支持這一點：

that you actually do get the virus evolving towards mildness.

我們確實使病毒不斷進化成溫和的病毒.

And that will just add to the effectiveness of our control efforts.

這會使我們的控制方法更有效.

So the other thing I really like about this,

另一個讓我喜歡這主意的原因是,

besides the fact that it brings a whole new dimension

除了對控制疾病研究帶來

into the study of control of disease,

一個全新層面的領域之外,

is that often the kinds of interventions that you want,

通常這種我們想要的人為干預

that it indicates should be done,

也就是我們該做的事,

are the kinds of interventions that people want anyhow.

也是大家都非常希望想要的干預.

But people just haven't been able to justify the cost.

但是人們還無法判斷其成本是否合理。

So, this is the kind of thing I'm talking about.

因此，這也是我想提的.

If we know that we're going to get extra bang for the buck from providing clean water,

如果我們知道提供清潔的水源,我們會得到額外的好處.

then I think that we can say,

那麼我認為我們會說

let's push the effort into that aspect of the control,

讓我們努力推廣這方面的的控制,

so that we can actually solve the problem,

這樣我們就能真正解決問題.

even though, if you just look at the frequency of infection,

即使當你仔細研究傳染病的發生率時,

you would suggest that you can't solve the problem well enough

你或許會說僅靠清潔水源無法

just by cleaning up water supply.

完全解決問題,但也值得去實行.

Anyhow, I'll end that there, and thank you very much.

好!我就講到此,非常感謝大家.

(Applause)

拍手!