For most of human history, medical workers sought to treat diseases or cure them.
在人类史中的大多数时候，医疗工作者都在努力治疗或治愈疾病。
The rise of vaccination in the 19th century enhanced the potential to prevent people from contracting illnesses in the first place.
19世纪疫苗接种的普及显著地增强了人们对于疾病的预防。
But only in recent decades did it become possible to ensure that a particular disease never threatens humanity again.
但仅仅也是在最近几十年，确保某种疾病不再对人类构成威胁才成为可能。
The story of smallpox, the first and, so far, the only disease to be permanently eradicated from the world,
天花，这个截至目前唯一一个在世界上被永久根除的疾病，
shows how disease eradication can happen and why it is so difficult to achieve.
它的故事表明了根除疾病是怎样实施的以及为什么如此困难。
Smallpox emerged in human populations thousands of years ago as a contagious virus that spread rapidly,
天花数千年前已经侵入人类，作为一种传染性疾病，它传播很快，
primarily through close, face to face contact, causing fever, aches and rashes.
主要通过近距离的互相接触，引起发烧、疼痛、皮疹。
It killed up to 30% of its victims and often left survivors with life-long disfiguring scars.
患者中的30%因此死亡，而且通常幸存者也不得不忍受长达一生丑陋的伤疤。
The devastating impact of smallpox was so great that several cultures had religious deities specifically dedicated to it.
天花灾难性的影响如此之大，以至于数种文化中都有专门的神诋来负责它。
In the 20th century alone, it is estimated to have killed more than 300 million people worldwide.
仅在20世纪，据估计全世界就有3亿人因此死亡。
With the effective deployment of vaccination, the number of cases began to decrease.
随着疫苗接种的有效应用，疫情人数开始减少。
By seeking out infected individuals, isolating them, and vaccinating their contacts to prevent further transmission,
通过寻找被感染的人隔离他们，阻止他们与他人的接触来防止进一步传播，
scientists realized that the spread of the disease could be haulted.
科学家发现疾病的传播可以得到中止。
In fact, because smallpox could only survive in human hosts,
实际上，因为天花只能通过人类宿主生存，
vaccinating all of an infected persons' potential contacts would stop the virus dead in its tracks and eliminate it from that region.
对受感染者所有可能接触的人群都进行疫苗接种，可以切断病毒的传播渠道，将它从特定区域消灭。
Once this strategy had succeeded in ridding most industrialized countries from disease,
一旦这种策略成功地在大多数工业国家消除了病毒，
health officials realized that eradicating it worldwide was within reach.
卫生人员就意识到了在全球范围内根除病毒是可能的。
But this was not an easy process, proving especially difficult in places suffering from poor infrastructure or civil wars.
但路漫漫其修远兮，特别是在卫生基建设施匮乏的地区尤为困难，另外也受阻于人类间的内战。
The eradication effort took decades and involved millions of people working together,
根除病毒的努力持续了几十年，数百万人民团结一心，奋发努力，
from world leaders and international organizations to rural doctors and community workers.
不论是世界领袖和国际组织，还是乡下郎中和社区工作人员。
In India, one of the last strongholds of the disease,
在印度，病毒最后一个据点之一，
health workers visited every one of the country's 100 million households to search for cases.
卫生工作者走访了这个国家一亿家庭中的每一个，来搜寻受感染案例。
Through this unprecedented worldwide effort, in which even rival superpowers cooperated,
通过这次史无前例的全球动员，包括对立的超级大国也互相合作，
smallpox was finally declared eradicated in 1980, saving approximately 40 million lives over the following two decades.
最终在1980年天花被宣告根除，在接下来的二十年里挽救了大约四千万人口。
There were several factors that made smallpox an ideal candidate for eradication.
这里面有几个因素让天花成为能够被根除的病毒中的一个理想案例。

First, humans are essential to the smallpox lifecycle,
第一，人类是天花存在的基础，
so breaking the chain of human to human transmission causes the virus to die out.
所以切断人与人之间的传播链会让病毒逐渐灭亡。
In contrast, many other pathogens, like ebola or the bubonic plague, can survive in animal carriers,
相反，许多其它病原体，比如埃博拉或腺鼠疫，能够在动物宿主中存活，
while the bacteria that cause tetanus can even live in the soil.
破伤风细菌甚至能在土壤中存活。
Secondly, individuals infected with smallpox displayed a characteristic rash,
第二，天花的受感染者会出现特征性皮疹，
making them easy to identify, even without a lab test.
这让他们很容易被区分，即使不用实验测试也可以辨别。
The lack of such practical diagnostic tools for diseases with non-specific symptoms, or that have long incubation periods,
但如果缺乏实用诊断工具，对于非特异性症状或者长期潜伏的疾病，
such as AIDS, makes their eradication more difficult.
比如艾滋病，会增加根除它们的难度。
Third, the availability of a smallpox vaccine that provided immunity for five to ten years in a single dose
第三，天花疫苗的出现，单次剂量就能提供5到10年的免疫，
meant that there was an effective intervention to stop the virus from spreading.
这意味着有效地控制了病毒的传播。
And finally, the initial success of several countries in eliminating the disease within their borders
最后，最初几个成功的国家在自己的国家内消灭了疾病，
served as a proof of principle for its eradication worldwide.
成为了在全世界根除该疾病的样例。
Today, the same criteria are applied to determine whether other diseases can be similarly eliminated.
现在，同样的标准被用来判定其它的疾病是否能够一样被消除。
And even though smallpox remains the only success story thus far, several other pathogens may be next in line.
尽管目前天花是唯一一个成功的案例，其它几个病原体将会成为接下来几个成功的例子。
Great progress has been made towards eradicating guinea worm disease simply by use of water filters.
根除麦地那龙线虫病已经取得了巨大的成果，靠得只是使用净水过滤器以及针对小儿麻痹症的疫苗。
And vaccination for polio, which previously disabled hundreds of thousands of people each year
这种疾病之前每年都伤害成百上千人，
is estimated to have prevented 13 million cases of paralysis, and 650,000 deaths since 1988.
据估计自1988年起，大家的努力已让一千三百万人口免于瘫痪，让六十五万人口免于疾病死亡。
With a 99% drop in infections since the eradication effort began,
自从消灭疾病活动开展以来，受感染率下降了99%，
one final push is all that is needed to ensure that polio will never paralyze another child.
最后一击就是确保将来不会有脊髓灰质炎导致任何一个孩子瘫痪。
Disease eradication is one public health effort
消灭疾病是一项公众卫生运动，
that benefits all of humanity and challenges us to work together as a global community.
全人类皆受益，也挑战着我们能否携手前行，一起抗击病毒。
Beyond eliminating specific diseases, eradication programs benefit local populations by improving health infrastructure.
在消灭特定病毒之外，该项目也能够通过提高卫生基础设施水平让当地人民受益。
For example, Nigeria recently used facilities and personnel from their polio eradication program to effectively control an ebola outbreak.
比如，尼日利亚最近使用的设施和人员就来自小儿麻痹症根除项目，有效地控制了埃博拉的爆发。
Further more, globalization and international travel
更进一步，全球化和国际旅行，
means that even a single infection anywhere in the world can potentially spread to other regions.
意味着在任何地方的唯一一次感染就有可能扩散给其它区域。
By helping to protect others, we help to protect ourselves.
帮助他人，也是在帮助我们自己。
Disease eradication is the ultimate gift we can give to everyone alive today, as well as all future generations of humanity.
消灭疾病是给现在活着的人和我们的子孙后代最好的礼物。