We live in an interconnected, an increasingly globalized world.
我们生活在互相联系越来越频繁的世界里。
Thanks to international jet travel,
因为国际航班，
people and the diseases they carry can be in any city on the planet in a matter of hours.
无论人类还是疾病，都能被带到任何地方，到地球上的任何一个城市，也不过十几个小时而已。
And once a virus touches down, sometimes all it takes is one sneeze to spread the infection throughout the community.
而一旦病毒登陆，有时只需一个小喷嚏，就能使整个社区被病毒感染。
When humans were hunter-gatherers, roaming the wild savannas, we were never in one place long enough,
当还是野人时，大家在野生热带树林里狩猎，从不会在一个地方停留过久，
and settlements were not large enough to sustain the transmission of infectious microbes.
而且他们居住地也不大，从而防止病菌传播。
But with the advent of the agricultural revolution 10,000 years ago,
在一万年前，随着农业革命的出现，
and the arrival of permanent settlements in the Middle East,
中东地区人类的居住地逐渐出现，
people began living side-by-side with animals,
使人们开始与动物生活在同一屋檐下，
facilitating the spread of bacteria and viruses between cattle and humans.
促进了牲畜与人类之间细菌和病毒的传播速度。
Epidemics and pandemics come in many shapes and forms.
传染病和流行病来自于各种形式。
In 2010, for instance, a devastating earthquake struck Haiti, forcing thousands of people into temporary refugee camps.
例如，2011年毁灭性的地震袭击了海地，迫使数以万计的海地人民要住在临时的难民营，
Within weeks, the camps had become breeding grounds for cholera,
在几个星期内，难民营就发生了霍乱，
a bacteria spread by contaminated water, triggering a country-wide epidemic.
这是一种通过污染水源传播的疾病，它诱发了遍及全国的传染病。
But the most common cause of epidemics are viruses, such as measles, influenza and HIV.
但是传染病最普遍的病原体是病毒，例如麻风病毒，流行性感冒和艾滋病病毒。
And when they go global, we call them pandemics.
当它们走向全球，我们把它们称作流行病。
