you probably think of something like this.

你可能會想到這樣的事情。

A barn,

一個穀倉。

a field,

a場。

a diverse group of animals…

種類繁多的動物...

Until relatively recently, if you ate meat,

直到最近，如果你吃肉。

it probably came from a farm that looked basically like this.

它可能來自一個農場，看起來基本上是這樣的。

And that was true around the world.

而全世界都是如此。

But in the last few decades, the global production of meat has skyrocketed.

但在過去的幾十年裡，全球肉類的產量急劇上升。

And that's been driven by a change in how livestock is raised.

而這是由牲畜飼養方式的改變所推動的。

In order to increase profits and raise livestock more cost-effectively,

為了增加利潤，提高畜牧業的成本效益。

farms like this one started to consolidate and to mechanize.

像這樣的農場開始整合和機械化。

Take chicken farms for example.

以養雞場為例。

In the 1970s, the US had around 30,000 chicken farms.

20世紀70年代，美國約有3萬個養雞場。

By 1995, it had only about 20,000.

到1995年，它只有2萬人左右。

But the amount of chicken produced in the US had tripled.

但美國的雞肉產量卻增加了三倍。

This is what one of those consolidated farms looks like.

這就是其中一個綜合農場的樣子。

Farms like this are controversial.

這樣的農場是有爭議的。

There are ethical concerns,

有道德問題。

environmental concerns...

環境問題...

But infectious disease experts worry about them for a different reason.

但傳染病專家擔心它們的原因卻不同。

A farm like this is called a concentrated animal feeding operation, or CAFO.

像這樣的農場被稱為集中式動物飼養場，或CAFO。

CAFOs are basically huge industrialized farming operations.

CAFO基本上是巨大的工業化養殖場。

They contain tens of thousands of animals, sometimes hundreds of thousands of animals,

它們包含了數萬只動物，有時甚至是數十萬只動物。

and they're often very crowded.

而且他們往往非常擁擠。

American CAFOs were efficient and profitable.

美國的CAFO效率高，利潤高。

And soon, they became a model for farming all over the world.

而很快，他們就成了全世界養殖的典範。

Today, almost all the meat we eat comes from farms like this.

今天，我們吃的肉幾乎都來自這樣的農場。

Factory farms supply an estimated 90 percent of meat globally

據估計，全球90%的肉類由工廠化養殖場供應。

and around 99 percent of the meat we eat here in the US.

以及我們在美國吃的99%左右的肉。

So if you're eating a burger or bacon or whatever it is today,

所以如果你今天吃的是漢堡或者培根什麼的。

it probably came from a factory farm.

它可能來自一個工廠化的農場。

A CAFO is an environment built for one purpose: to house as many animals as possible.

CAFO是為一個目的而建造的環境：儘可能多地容納動物。

What worries scientists is that that also makes it an ideal environment

令科學家們擔心的是，這也使它成為一個理想的環境。

for the pathogens that cause pandemics.

為導致大流行病的病原體。

A virus is really just a bit of genetic code that makes copies of itself.

病毒其實就是一點遺傳密碼，它可以複製自己。

But that replication process isn't always perfect.

但這個複製過程並不總是完美的。

They're introducing lots of mutations as they replicate.

他們在複製的過程中引入了大量的變異。

Martha Nelson studies viruses at the National Institutes of Health.

瑪莎-尼爾森在美國國立衛生研究院研究病毒。

Most of those mutations are going to be deleterious and won't help the virus at all.

這些突變大部分都會是有害的，對病毒一點幫助都沒有。

Lots of mutations just lead to the virus dying.

大量的變異只是導致病毒死亡。

But occasionally, a mutation will happen that will give the virus a new ability:

但偶爾也會發生突變，讓病毒有新的能力。

to be more deadly, for example, or to be able to jump from one species to another.

例如，為了更加致命，或者能夠從一個物種跳到另一個物種。

A virus can only replicate when it's inside another organism — a host.

病毒只有在另一個生物體--宿主體內才能複製。

But it can only replicate inside a host for so long. Every host eventually dies.

但它只能在主機內複製這麼久。每個宿主最終都會死亡

That means, even if a virus does mutate in a beneficial way,

這意味著，即使病毒真的發生了有益的變異。

without hosts, that mutation will eventually die out.

沒有宿主，這種變異最終會消亡。

And out in the wild, or even on a small farm, new hosts can be hard to come by.

而在野外，甚至在一個小農場裡，新的主人可能很難出現。

But in a CAFO...

但在CAFO...

Let's say you're a pathogen. If you're in a factory farm,

比方說，你是一個病原體。如果你在工廠化養殖場。

where you have hundreds of thousands of potential hosts, it's a bonanza.

在那裡你有幾十萬個潛在的主機，這是一個大好機會。

More hosts, means more chances to replicate, more chances to mutate,

更多的宿主，意味著更多的複製機會，更多的變異機會。

and a higher likelihood that a mutated virus will survive.

和變異病毒存活的可能性更高。

In other words, factory farms are also factories for new viruses that we haven't seen before.

換句話說，工廠化養殖場也是我們沒見過的新病毒的工廠。

And that's also helped along by the larger system that CAFOs are part of.

而這也得益於CAFO這個大系統的幫助。

There's a lot of international trade going on of live animals.

有很多活體動物的國際貿易。

We're sending these animals from city to city and from country to country.

我們把這些動物從城市送到城市，從國家送到國家。

We're flying them across oceans.

我們要讓他們飛越大洋。

Some viruses have a genetic code that's segmented into parts.

有些病毒的遺傳密碼被分割成若干部分。

And sometimes, two of these viruses come into contact with each other.

而有時，其中的兩種病毒會相互接觸。

Occasionally, you can have two separate viruses co-infect a single cell.

偶爾，你可以讓兩個獨立的病毒共同感染一個細胞。

When they replicate, they can just kind of swap out entire segments with the other virus.

當他們複製的時候，他們可以和其他病毒交換整個片段。

And through that, you can kind of create these chimeric, you know, offspring that have pieces

通過這種方式，你可以創造這些嵌合體，你知道，後代有碎片的地方

from the two parents.

從雙親。

Just like with mutations, this swapping and shuffling of segments between viruses is basically random.

就像突變一樣，這種病毒之間的片段交換和洗牌基本上是隨機的。

And that means sometimes the new virus is a dud.

而這意味著有時新病毒是個啞巴。

But every now and then, you hit jackpot, and you come up with a radically new combination

但每隔一段時間，你就會中大獎，你就會想出一個全新的組合。

that has properties that neither of the two parents had.

具有父母雙方都沒有的屬性。

In CAFOs, viruses have an opportunity to come into contact with each other all the time.

在CAFO中，病毒有機會隨時接觸對方。

That's making it easier for a virus that exists over here on one side of the world

這使得病毒更容易存在於世界的另一邊。

that normally would just stay on that side of the world,

通常只會停留在世界的那一邊。

to travel quite quickly to another part of the world.

迅速前往世界的另一個地方。

With viruses from different parts of the world mixing and shuffling and mutating inside animals,

隨著來自世界各地的病毒在動物體內混合洗牌、變異。

humans have made it very easy for a nasty virus to emerge.

人類讓一種惡劣的病毒很容易出現。

And actually, it's happened already.

而實際上，它已經發生了。

“We are continuing to closely monitor the emergency cases of the H1N1 flu virus."

"我們正在繼續密切監測H1N1流感病毒的緊急病例"。

In 2009, a new virus quickly spread around the world.

2009年，一種新的病毒迅速在全球蔓延。

It became known as the "swine flu" because of its links to pig farms in North America.

由於它與北美的養豬場有關，所以被稱為 "豬流感"。

It came from the major swine production region that's right outside of Mexico City.

它來自墨西哥城外的主要生豬產區。

That particular virus was able to evolve there because you had pigs

這種特殊的病毒能夠在那裡進化，因為你有豬。

coming from the United States over the border into Mexico. You have pigs from Europe.

從美國越過邊境進入墨西哥。你有來自歐洲的豬。

And so you have this sort of mixing bowl of pigs from all over the world that are able to share their viruses

所以你有這種混合碗 來自世界各地的豬 能夠分享他們的病毒。

and exchange genetic components and create this really unusual pandemic variant.

和交換基因成分，並創造出這種真正不尋常的大流行變種。

By the time public health measures and a vaccine were able to get it under control,

到了公共衛生措施和疫苗能夠控制住。

swine flu had killed hundreds of thousands of people.

豬流感已造成數十萬人死亡。

But viruses are just one kind of pathogen that CAFOs are really good at incubating.

但病毒只是CAFO真正擅長孵化的一種病原體。

Because bacterial disease can spread so easily in a CAFO,

因為在CAFO中，細菌病很容易傳播。

farmers typically treat their livestock with antibiotics, which limits the bacteria's spread.

農民通常用抗生素治療牲畜，這樣可以限制細菌的傳播。

And often, every animal gets that antibiotic — whether they're sick or not.

而往往每個動物都會得到這種抗生素--不管它們是否生病。

At first, that prevents bacterial disease from running rampant through the population.

起初，這樣可以防止細菌性疾病在人群中肆虐。

But over time, just like viruses, bacteria will mutate.

但隨著時間的推移，就像病毒一樣，細菌也會發生變異。

The antibiotic will kill most of those mutations

抗生素會殺死大部分的突變物。

unless the mutation gives them the ability to resist it.

除非變異讓他們有能力抵抗。

And over time...

而隨著時間的推移...

As the bacteria evolve, those that have the mutation to survive the antibiotic

隨著細菌的進化，那些有突變的細菌在抗生素的作用下生存下來。

will become more and more dominant.

將會變得越來越主要。

This is how we end up with antibiotic-resistant bacteria.

這就是我們如何最終獲得抗生素耐藥性的細菌。

And that becomes really dangerous if it spreads into humans.

而如果傳播到人類身上，就會變得非常危險。

And so then when we humans come along and try to treat the bacteria with antibiotics

所以當我們人類出現並試圖用抗生素治療細菌時

in our own bodies, the bacteria might not respond to those antibiotics.

在我們自己的身體裡，細菌可能對這些抗生素沒有反應。

One way to lower the risk of CAFO-borne pathogens would be to change the CAFO system to make

降低CAFO傳播病原體風險的方法之一是改變CAFO系統，使之成為

the spread of pathogens harder.

使病原體的傳播更加困難。

We could decrease the long-distance transport of live animals.

我們可以減少活體動物的長途運輸。

We could have smaller and less crowded farms,

我們可以有更小更不擁擠的農場。

so that pathogens don't have so much opportunity to rip through huge numbers of animals.

這樣，病原體就不會有那麼多的機會去撕咬大量的動物。

But making CAFOs safer for humans wouldn't address other concerns about them,

但讓CAFO對人類更安全，並不能解決對它們的其他擔憂。

like animals' quality of life, or the lagoons of liquid manure they produce.

如動物的生活品質，或它們產生的液態糞便的瀉湖。

Ending CAFOs entirely, and returning to a smaller model of farming, would.

徹底結束CAFO，迴歸到小規模的農業模式，將：

It's actually entirely possible for us to have a meat production system that is better

其實我們完全有可能擁有一個更好的肉類生產系統。

for human health as well as for the climate and for the animals themselves.

對人類健康、氣候和動物本身都有好處。

We just need to abandon factory farming to get that.

我們只需要放棄工廠化養殖就可以了。

We could also just eat less meat.

我們也可以少吃點肉。

After all, the amount of meat we eat today is a recent development.

畢竟，我們今天吃的肉量是最近才發展起來的。

But now that we know what it's like to experience a pandemic,

但現在我們知道了經歷大流行的感覺。

we should understand the risks of the animal pathogens cooking in our food systems.

我們應該瞭解在我們的食物系統中烹調的動物病原體的風險。

It's just a matter of time before one ends up in the human population.

最後淪為人類人口中的一員，只是時間問題。

Whether that happens next year, whether that happens in a decade,

無論明年是否發生，無論十年後是否發生。

that's a crystal ball. We don't know.

那是一個水晶球。我們不知道。

But we do know that we are playing with probabilities.

但我們知道，我們是在玩概率。

And we're continually increasing the probability

而且我們在不斷地增加概率。

as we increase the pool of viruses in these farms.

由於我們增加了這些養殖場的病毒庫。