感的人的尸体组织后，证明了禽流感是同一种病毒的现代变异体。

自从地球上有了生命，便有了细菌和病毒。当今的很多疾病存在的时间和人类历史一样长。我们有必要回顾一下历史上疾病的传播情况，从而弄清楚传染病的起因和后果，并且希望将来能够预防它们的发生。

One of the earliest epidemics on record⑮ happened about 500－550 AD when the Roman emperor at the time was attempting⑯ to rebuild⑰ the Roman Empire.This epidemic swept through⑱ North Africa, the Middle East and Europe.

Scientists now guess that up to⑲ 50% of the area's population died from this epidemic ⑳making it one of the main causes of the fall of the Roman Empire○21.

In the 1330's, the epidemic returned, this time in Asia.It spread rapidly and became known as "The Black Death" as one symptom○22 was black spots on the body○23. The conditions in much of Asia and Europe - war, crowded○24 cities and a lack of○25 basic health routines○26 - provided the perfect conditions for the disease to spread worldwide.

In urban○27 areas all over Europe, Asia, Africa and the Middle East, up to one half of the population was lost to the Black Death.

⑮on record正式记录的，公开发表的

⑯attempt to do试图做

make an attempt to do sth./at doing sth.试图做某事

⑰rebuild/ˌriː'bIld/vt.重建

⑱sweep through席卷；顺利通过

⑲up to达到(数量、程度等)；至多

⑳making it one of the main causes ...是现在分词短语作结果状语。

○21empire/'empaIə/n.帝国

○22symptom/'sImptəm/n.症状

○23as one symptom was black spots ...是as引导的原因状语从句。

○24crowded adj.拥挤的　　be crowded with挤满了......

○25a lack of缺乏，不足 for lack of由于缺乏，因缺乏

○26routine/ruː'tiːn/n.常规；惯例

○27urban/'ɜːbən/adj.城市的

[第4～7段译文]

历史上有记载的最早的传染病之一发生在公元500～550年，当时的罗马皇帝正在试图重建罗马帝国。这次瘟疫席卷了北非、中东和欧洲。

现在科学家们猜测，当时那一地区百分之五十的人口死于那场瘟疫，使之成为罗马帝国衰落的主要原因之一。

14世纪30年代，这种瘟疫又爆发了，这次是在亚洲。疾病传播迅速，被人们称为"黑死病"，因为一个病症是病人身体上出现黑色斑点。当时亚洲和欧洲的大部分地区都陷入这样的状况--战争频发，城市拥挤不堪，缺乏基本的健康体系，这种 状况促进了瘟疫在全球范围内的蔓延。

在欧洲、亚洲、非洲和中东的城市地区，有一半的人死于黑死病。

Another epidemic that spread in similar conditions was the Great Flu Epidemic of 1918, also called the Spanish Flu. It struck○28 near the end of the First World War and left families mourning○29 worldwide.

Having killed up to 50 million people in 18 months○30，with a tendency to strike