The real reason polio is so dangerous

譯者: Lilian Chiu 審譯者: Ruan Xiu Ze 阮修泽

In 1952, polio was everywhere.

在 1952 年，小兒麻痺處處可見。

For years, this virus killed or paralyzed roughly half a million people annually,

數年來，此病毒每年造成 約五十萬人死亡或癱瘓，

leaving survivors reliant on crutches, wheelchairs, and respirators.

存活者也得依靠拐杖、 輪椅、和呼吸器才能生活。

Yet just 10 years later, paralytic polio cases in the US dropped by 96%.

但僅僅十年後，

美國的癱瘓性小兒麻痺 病例數就下降了 96%。

Soon, similar trends spread worldwide,

沒多久，世界各地 都出現類似的趨勢，

and it looked like we were on track to eradicate polio for good.

看起來我們很有希望 可以讓小兒麻痺永遠消失。

But in the 21st century, the virus started striking back.

但在二十一世紀， 這些病毒開始反擊。

So, what’s the source of these recent spikes,

近年來病例激增的原因是什麼？

and how can researchers fighting polio finally get rid of this deadly disease?

研究小兒麻痺的專家又該如何 根除這種致命的疾病？

To answer these questions, we first need to understand the true danger of polio.

要回答這些問題，我們就得 了解小兒麻痺真正的危險性。

Most infected individuals only present mild flu symptoms or no symptoms at all,

大部分受到感染的病人 都只是呈現出輕微的流感症狀

或完全沒有症狀。

with paralysis occurring in less than 1% of cases.

只有不到 1% 的病人會癱瘓。

Which is why the real danger of polio is how infectious it is.

這就是為什麼，小兒麻痺真正的 危險性在於它的傳染性很強。

Historically, there have been three strains of poliovirus,

歷史上，小兒麻痺病毒 共有三種病毒株，

all of which typically enter our mouths from airborne droplets

通常都是透過空氣中的飛沫 進入我們的嘴巴，

or contact with infected fecal matter.

或是接觸到受感染的糞便而被傳染。

This means polio runs rampant in communities with poor sanitation.

意即，小兒麻痺會在 衛生條件差的社區內肆虐。

And once infected, individuals remain contagious for 3 to 6 weeks,

受到感染的個體在感染後的 三到六週都具有傳染性，

spreading a silent outbreak with few trackable symptoms.

疫情就這樣靜靜地蔓延開來， 沒有幾個症狀是可以追蹤的。

This is what made polio unstoppable

這就是為什麼小兒麻痺很難阻擋，

until US physician Jonas Salk found a solution in the early 1950s.

直到 1950 年代初期，美國醫生 約納斯‧沙克發現了解決方案。

He created an inactivated version of the virus that, when injected,

他創造出此病毒的非活性版本，

注射到人體後，

prevented all three strains from causing paralysis.

可預防所有三種病毒株引起癱瘓。

However, this inactivated poliovirus vaccine, or IPV,

然而，這種非活性 小兒麻痺病毒疫苗（IPV）

didn’t stop poliovirus from living in our bodies and spreading to others.

無法阻止小兒麻痺病毒在我們 體內存活及傳播給其他人。

Fortunately, Polish American microbiologist Albert Sabin

幸運的是，波蘭裔美國 微生物學家亞伯特‧沙賓

was creating the oral polio vaccine, or OPV, at the same time.

同時也創造出口服的 小兒麻痺疫苗（OPV）。

This even cheaper and easier to administer treatment

這種治療方法更便宜也更容易施用，

contained weakened variants of each poliovirus strain,

內含有各種小兒麻痺 病毒株的弱化變異株，

known as attenuated viruses,

也就是所謂的減毒病毒。

And once ingested, these prevented polio from settling in the body altogether.

攝入後，就可以防止 小兒麻痺病毒存留體內。

Over the next several decades,

在接下來的數十年，

IPV and OPV eliminated polio in country after country.

IPV 及 OPV 在一個又一個 國家中消滅了小兒麻痺。

But near the turn of the century,

但在世紀之交將至時，

this arms race between medical ingenuity and viral evolution took a turn.

這場醫療創新與病毒演化 之間的軍備角力出現了轉折。

Scientists discovered variant strains of polio—

科學家發現了小兒麻痺 病毒變異株——

each almost identical to one of the three existing strains.

且幾乎都和既有的 三種病毒株之一相同。

And their source was even more troubling.

它們的來源更讓人擔憂。

Up to this point, one of OPV’s greatest advantages was that its attenuated viruses

在此之前，OPV 的一大優勢

在於其減毒病毒可以像瘋狂的 小兒麻痺病毒那樣傳播，

could spread just like wild polio,

moving through the air and immunizing unvaccinated individuals.

透過空氣移動，

讓未接種的個體也能免疫。

But researchers discovered that if these weakened viruses circulated

但研究者發現，如果這類弱化病毒

在接種比例低的群體中 循環傳播幾週，

for several weeks in under-vaccinated populations,

they could mutate into new vaccine-derived strains.

就有可能突變， 成為新的疫苗衍生株。

To be clear, this didn’t mean the attenuated vaccine

澄清一下，這並不表示減毒疫苗

was inherently dangerous.

在本質上是危險的。

OPV had already been used to stop wild poliovirus type 2 worldwide

OPV 已經在世界各地被用來阻止 野生小兒麻痺病毒第二型，

and eradicate all wild poliovirus

還將下列各地的所有 野生小兒麻痺病毒都根除了：

from the Americas, West Pacific, and countless other countries.

美洲、西太平洋，及其他無數國家。

The issue was ensuring populations met a certain vaccination threshold—

問題點在於要確保對象群體 有達到某種疫苗接種標準——

specifically, at least 80% of every community needed to be vaccinated

明確來說，每個社區 都至少要有八成的人接種疫苗，

to prevent strains from mutating.

才能預防病毒株突變。

So, in our current fight against polio,

在我們目前對抗小兒麻痺的抗戰中，

we've taken two approaches to this problem.

我們採用兩種方法來處理這個問題。

First, vaccine developers have made even safer forms of OPV.

第一，疫苗開發者已經 製造出更安全型的 OPV。

Monovalent and bivalent OPVs

單價和雙價 OPV 分別

respectively contain one or two types of attenuated poliovirus,

含有一或兩種減毒的小兒麻痺病毒，

reducing the number of strains that could possibly mutate.

減少可能突變的病毒株數目。

These vaccines helped eradicate wild poliovirus types 2 and 3,

這些疫苗能協助根除野生 小兒麻痺病毒第二和第三型，

and today they’re tackling the last remnants of type 1 poliovirus

現今，它們正在巴基斯坦 和阿富汗對付殘存的

in Pakistan and Afghanistan.

小兒麻痺病毒第一型。

Vaccine researchers also developed OPVs targeting vaccine-derived polio.

疫苗研究者也針對疫苗衍生 小兒麻痺開發出了 OPV。

Currently, most polio cases are caused by vaccine-derived poliovirus

目前，大部分的小兒麻痺病例都是 疫苗衍生小兒麻痺病毒第二型所致，

type 2 outbreaks in Africa and the Middle East.

源自非洲和中東的疫情。

So researchers created a new vaccine specifically to tackle this strain

因此研究者針對這種病毒株 創造了新的疫苗，

with minimal risk of mutating.

並把突變風險降到最低。

Second, medical workers on the front lines are using cutting-edge technology

第二，前線醫療工作者 現在會使用先進技術

to ensure every population meets that 80% threshold.

來確保所有疫苗的對象群體 都有滿足八成已免疫的標準。

Digital tools like geospatial imaging and analysis

地理空間影像和分析等數位工具

help them locate and immunize remote communities.

讓他們能找到偏遠社區所在 並協助居民免疫。

Extensive monitoring systems ensure they don’t miss a single child.

廣泛的監視系統能確保 他們不會漏掉任何一個孩子。

And waste surveillance systems employed across the globe

全球各地採用的廢物監測系統

can alert us to potential outbreaks.

也能警示我們可能發生的疫情爆發。

Today, the fight against polio is at a critical moment.

現在，對抗小兒麻痺的抗戰 來到了關鍵時刻。

We’re primed to eradicate wild poliovirus in the near future,

我們已經準備好在不久的將來 根除野生小兒麻痺病毒，

and with our new vaccines,

有了新的疫苗，

eradicating vaccine-derived strains might not be much further off.

可能不用太久也能夠實現 根除疫苗衍生病毒株的夢想。

But doctors still struggle to reach areas

但醫生還很難

到達發生軍事衝突 和內部動亂的地區，

experiencing military conflict and civil unrest.

And without keeping vaccination rates high,

若無法保持高免疫率，

polio’s silent outbreaks could easily surge.

小兒麻痺疫情很有可能 會再靜靜地爆發。

So it’s essential that we keep up the pressure

因此，重要的是，我們不能鬆械，

to finally finish what we started over 70 years ago.

必須要把我們在七十多年前 起頭的事情給做個了結。