continues to spread worldwide,

繼續在世界範圍內傳播。

one common theory is that the pandemic

一種常見的理論是，該大流行

will die down when warmer weather arrives.

當溫暖的天氣到來時，將逐漸消失。

Donald Trump: Looks like by April, you know,

唐納德・特朗普看起來像四月，你知道。

in theory, when it gets a little warmer,

理論上，當它變得更溫暖一些。

it miraculously goes away.

它奇蹟般地消失了。

I hope that's true.

我希望這是真的。

Narrator: But the answer

旁白：但答案是...

is a little more complicated than that.

是比這更復雜一些。

So, why do so many people think that summer

那麼，為什麼有那麼多人認為，夏

will stop the COVID-19 spread?

將阻止COVID-19的傳播？

Seasonal patterns are commonplace

季節性模式是常見的

for many infectious diseases.

對於許多傳染病。

Take the flu, for example.

以流感為例。

Jeffrey Shaman: We get these big surges of seasonal flu

傑弗裡-沙曼We get these big surges of seasonal flu (季節性流感)

that peak in January and February

1月和2月達到高峰

in the Northern Hemisphere

在北半球

and then the opposite side of the year,

再到當年的對面。

in July and August, in the Southern Hemisphere,

7、8月份，在南半球。

places like Australia, New Zealand, South Africa.

澳洲、紐西蘭、南非等地。

So the question has been why,

所以問題一直是為什麼。

and there are three groups of hypotheses

並有三組假設

that have tried to explain this.

試圖解釋這一點的。

Narrator: The first of these hypotheses

旁白：這些假設中的第一個

is human behavior.

是人的行為。

The flu spreads more in colder seasons,

流感在寒冷的季節裡傳播的更多。

when people are more likely to gather in enclosed spaces,

當人們更容易聚集在封閉的空間裡。

and lowers once people venture outside.

並在人們冒險外出後降低。

However, COVID-19 appears to spread

然而，COVID-19似乎傳播了

much more efficiently than the flu,

比流感更有效。

which is why strict physical-distancing laws

所以，嚴格的物理距離法則

have been enforced,

已執行。

but also why you may have heard experts

但也是為什麼你會聽到專家

warn of a rise in cases

警惕案件的增加

once people go back to their offices, schools

一旦人們回到辦公室，學校

and normal life.

和正常生活。

The second hypothesis has to do with your immune system.

第二個假設與你的免疫系統有關。

Immune systems have been found to be better

免疫系統已被發現是更好的

at fighting respiratory viruses

抵抗呼吸道病毒的能力

during longer summer days,

在較長的夏日裡。

which also increase the production

這也增加了生產

of the immunity booster vitamin D.

的免疫力增強劑維生素D。

So when summer rolls around,

所以當夏天來臨的時候。

people might have a better chance of fighting off

人多力量大

the coronavirus as well.

的冠狀病毒以及。

And also why you may have seen suggestions

也是為什麼你會看到建議

during this pandemic to spend time safely outdoors,

在這次大流行期間，要安全地在戶外活動。

for example, on a balcony or in your garden,

例如，在陽臺或花園裡。

or even to take vitamin D supplements.

甚至要補充維生素D。

But people have focused on the flu's

但人們把注意力放在了流感的

third seasonality hypothesis, the environment.

第三種季節性假說，環境。

That's because both COVID-19 and the flu

那是因為COVID-19和流感都是如此

are respiratory diseases

是呼吸道疾病

that can be spread through droplets.

可以通過液滴傳播的。

Once these droplets have been

一旦這些液滴被

coughed, sneezed, or spat out,

咳嗽、打噴嚏或吐痰。

they're in the hands of the environment

掌握在環境的手中

until they reach a new victim.

直到他們找到新的受害者。

Studies have found that the transmission levels

研究發現，傳播水準

decrease when the influenza virus encounters

減少，當流感病毒遇到

a humid and hot environment.

溼熱的環境。

That's the opposite of what we see during winter,

這與我們在冬季看到的情況正好相反。

where cold temperatures go hand in hand with dry air.

在這裡，低溫與乾燥的空氣並存。

One study found that when humidity levels

一項研究發現，當溼度水準

were at 23% after 60 minutes,

60分鐘後為23%。

70% to 77% of the flu virus survived.

70%～77%的流感病毒存活下來。

But when humidity increased to 43%,

但當溼度增加到43%時。

only 14% to 22% of the flu virus particles

只有14%至22%的流感病毒顆粒。

survived in the same amount of time.

在同樣的時間內存活下來。

Shaman: This humidity change seems to be

薩滿。這種溼度變化似乎是

modulating the survival of the virus,

調控病毒的生存。

such that it doesn't last as long in the summertime

以至於在夏天的時候，它不會持續那麼久。

and it lasts a much longer time

而它持續的時間更長

when it's drier in the wintertime.

冬天的時候比較乾燥的時候。

And that may encourage and allow the transmission,

而這可能會鼓勵和允許傳。

and hence we see these surges in the wintertime.

是以，我們在冬天的時候就會看到這些潮水。

Narrator: And scientists have a few answers

旁白：科學家們有了一些答案

as to why this is the case.

至於為什麼會出現這種情況。

The influenza virus is a simple genetic code

流感病毒是一個簡單的遺傳密碼。

surrounded by a protein layer and a fatty envelope,

由蛋白質層和脂肪包膜包圍。

similar to SARS-CoV-2,

與SARS-CoV-2相似。

the virus that caused COVID-19.

導致COVID-19的病毒。

But once it leaves the body,

但一旦離開身體。

a layer of water encapsulates it as well.

一層水也包裹著它。

Some scientists believe that in high-humidity environments,

有科學家認為，在高溼度環境下。

the virus picks up more water particles

病毒會帶走更多的水顆粒

and becomes heavier,

並變得更重。

which forces it to drop out of the air,

迫使它從空中落下。

lowering the chance of transmission.

降低傳播的機會。

In dry conditions, like in winter,

在乾燥的條件下，比如冬天。

those same droplets evaporate,

這些相同的液滴蒸發。

making the virus much lighter and airborne for longer.

使得病毒更輕，在空氣中傳播的時間更長。

But that evaporation has another

但這種蒸發還有另一種

positive transmission effect.

正向傳輸效應。

The water droplet and virus are not alone.

水滴和病毒並不孤單。

They are also joined by salts,

它們也是由鹽類加入的。

and one study found that as the water droplets

而一項研究發現，由於水滴

evaporate in the dry air,

在乾燥的空氣中蒸發。

those salts are removed,

這些鹽類被去除。

increasing the virus' stability

增加病毒的穩定性

and probability of transmission.

和傳播的概率。

But it's not just humidity that has an impact

但影響的不僅僅是溼度的問題

on the influenza virus.

關於流感病毒。

Researchers have found the virus to be

研究人員發現該病毒是

much more robust in colder temperatures too,

在低溫下也更加堅固。

lasting far longer than when exposed to higher temperatures.

比暴露在較高溫度下的時間要長得多。

So, by now, you may be thinking the flu and COVID-19

所以，到現在，你可能會認為流感和COVID-19。

are both respiratory infections

都是呼吸道感染

with somewhat similar structures,

結構有些類似。

so surely they will follow

定會跟上

similar seasonal patterns as well.

也有類似的季節性規律。

But let's be clear:

但我們要明確一點。

They're not the same.

它們是不一樣的。

Not only in transmission rates, symptoms, and death rates,

不僅在傳播率、症狀、死亡率。

but also in the length of time that they have existed

但也是在它們存在的時間長短上。

in human populations.

人群中。

This is pretty important to consider,

這是相當重要的考慮。

especially when you look at

尤其是當你看到

how virus transmissions slow down.

病毒傳播速度如何減慢。

Micaela Martinez: At the beginning of the high season,

Micaela Martinez。在賽季初

you have some big susceptible pool of individuals,

你有一些大的 易受影響的個人池。

and then as that epidemic rose and cases climbed,

然後隨著該疫情的上升和病例的攀升。

that susceptible pool's getting smaller and smaller

越來越小的易受影響的池的越來越小

and smaller and smaller,

並越來越小。

so when you get up here at the top,

所以，當你在這裡得到的頂部，

you have fewer people that can get infected.

你有更少的人，可以得到感染。

Narrator: You can think of this like kindling for a fire.

旁白：你可以把它想成是生火的火種

The longer the fire burns,

火燒得越久。

the more fuel is used,

使用的燃料越多。

so the less kindling you have,

所以你的火種越少。

and the fire will eventually begin to burn out.

而火最終會開始燃燒殆盡。

Both the smaller susceptible pool

既是較小的易感池

and the onset of the low season,

和淡季的來臨。

such as a rise in humidity,

如溼度的上升。

dictate when a disease's high season

審時度勢

begins to turn around.

開始轉身。

Martinez: That's very different from

Martinez：這跟

a pandemic situation,

疫情；

where you very well may have

在那裡你很可能已經

seasonal changes in transmission,

傳遞的季節性變化。

but then that's having to work essentially all by itself

但那就必須自己工作了

if there's not a shrinking of the susceptible pool

如果沒有易感人群的萎縮

that comes along with it.

隨之而來的。

Narrator: For a new viral pandemic like the current one,

旁白：像現在這樣的新病毒大流行病

the susceptible pool is huge.

易感池是巨大的。

Populations haven't developed immunity to it

人們對它還沒有形成免疫力。

like they have against, say, the flu.

就像他們對，比如說，流感。

And when you throw in a lack of vaccines and treatments,

而當你扔在缺乏疫苗和治療。

the fuel for the fire is almost endless.

火上澆油幾乎是無止境的。

This isn't to say that COVID-19 won't be hindered

這並不是說COVID-19不會受到阻礙。

at all by seasonality.

完全不受季節性影響。

One initial study from China showed decreases

一項來自中國的初步研究顯示，中國人的數量減少了

in SARS-CoV-2 transmission

在SARS-CoV-2傳播中

along with increases in humidity.

隨著溼度的增加。

However, another study

然而，另一項研究

wasn't able to establish that connection.

無法建立這種聯繫。

And both should be taken with a grain of salt

兩者都要慎重對待。

in the first place,

首先是。

as neither has been produced in a lab setting yet.

因為兩者都還沒有在實驗室環境中產生。

What could give a better insight

有什麼能給人更好的啟示呢？

are the ways in which

是如何

the four known common human coronaviruses,

四種已知的常見人類冠狀病毒；

which are partly responsible for the common cold,

這也是導致普通感冒的部分原因。

react to seasons.

對季節的反應。

Shaman: So, there's evidence from other coronaviruses,

薩滿所以，有證據 從其他冠狀病毒。

and all four of them do this,

而他們四個人都是這樣做的。

that they have this pronounced seasonality.

他們有這種明顯的季節性。

So there is this enticing possibility

所以有這個誘人的可能性

that has to be considered seriously

不得不說

and not dismissed

不置可否

that this novel coronavirus may also have this property

認為這種新型冠狀病毒也可能具有這種特性。

because it's related to them.

因為這與他們有關。

Narrator: But notoriously humid places,

旁白：但在眾所周知的潮溼的地方

such as Hong Kong and Louisiana,

如香港和路易斯安那州。

have seen prominent transmissions.

已經看到突出的傳輸。

And experts warn that when large groups

而專家警告說，當大群體

begin to gather again,

又開始聚集。

we could actually see another spike in cases,

事實上，我們可以看到另一個案件的高峰。

which brings us back to the fact

這使我們回到了這樣一個事實

that we may not see seasonal patterns just yet.

我們可能還看不到季節性的模式。

But this doesn't mean

但這並不意味著

that we won't see one in the future.

以至於我們在未來不會看到一個。

If and when COVID-19 becomes

如果COVID-19成為

a more regular presence in populations,

在人口中較為固定的存在。

there is a strong possibility of it being seasonal.

很有可能是季節性的。

As immunity, vaccines, and treatments

由於免疫力、疫苗和治療

become more readily available,

變得更容易獲得。

the susceptible pool will decrease,

易感池將減少。

and the spread will likely increase

和差價可能會增加

only when the conditions are more favorable

順其自然

and therefore seasonal.

是以是季節性的。

But, again, this is a new disease,

但是，這又是一種新病。

and these are only predictions.

而這些只是預測。

Current methods of stopping the outbreak

目前阻止疫情爆發的方法

such as self-isolation are far more efficient

如自我隔離的效率要高得多。

than waiting for it to stop naturally with the weather.

比起等待它隨著天氣的變化而自然停止。