In fact, although smallpox has been wiped out, in the 20th century over 30 previously unknown infectious diseases have emerged. They include the highly deadly ebola virus, hantaviruses and AIDS.
事實上，人類根除了天花，二十世紀卻出現了三十幾種前所未見的傳染病，其中包括：致命性極高的依波拉病毒、漢他病毒、愛滋病、新菌株引起的流行性感冒… … 等等。