Thus by the second half of the twentieth century, thanks to an apparently invincible medical science, humanity seemed to have become the absolute master of the natural world. So much so, that it began to let down its guard against viral disease-until 1981.
在無往不利的現代醫學保護下，二十世紀中葉開始，大半個世紀以來，人類似乎已成功擊敗微生物，取得了自然界完全獨霸的地位，對於傳染病的戒心也開始鬆弛──直到一九八一年。