enabled it to spread.

霍乱一直没有向外传播
The bacterium that causes cholera is extremely delicate

霍乱病毒非常脆弱
and doesn't travel so easily.

不易于传播
So, it required a number of factors that enabled the disease

所以需要一系列的条件使得
to move beyond its original area of endemicity.

霍乱病毒传播到它的最适区域之外
What were some of those? One was colonialism itself,

这些条件是什么呢第一个是殖民政策
which meant large-scale troop movements

也就是大量的军队流动
and increasing contact between the subcontinent

这使得次大陆和世界其他地方的
and the outside world.

联系愈发紧密
The increase in trade did the same thing in terms of increasing contact.

贸易的增加也起到了相似的作用
Then there was the transport revolution,

还有交通革命
which was very important.

这也是很重要的