OG11 阅读第二篇看不懂

小小鱼儿04

Although genetic mutations in bacteria and viruses can lead to epidemics，some epidemics are caused by bacteria and viruses that have undergone no significant genetic change．In analyzing the latter, scientists have discovered the importance of social and ecological factors to epidemics．Poliomyelitis，for example，emerged as an epidemic in the United States in the twentieth century by then，modern sanitation was able to delay exposure to polio Until adolescence or adulthood，at which time polio infection produced paralysis． Previously, infection had occurred during infancy, when it typically provided lifelong immunity without paralysis．Thus，the hygiene that helped prevent typhoid epidemics indirectly fostered a paralytic polio epidemic.

这第一个例子没有看懂，先是小儿麻痹症又说到伤寒去了，那现代医学是控制了小儿麻痹症还是使之加剧了？

AlienX

modern sanitation(=hygiene)有助防止typhoid epidemics, 可是indirectly fostered paralytic polio epidemic.  所以modern sanitation只是把poliomyelitis延遲發生...在有modern sanitation之前是在infancy時發生, 在有modern sanitation之後是在adolescence or adulthood時發生.

jetking

意思是过去医疗卫生条件差的时候，小儿麻痹通常在儿童时期就发病了，结果很多得病的人有了免疫，成年后瘫痪或者有残疾的症状或者几率很低；而现在医疗条件好了，阻止了很多小儿麻痹在儿童时期发病，结果导致这种发病延迟到成年以后，结果成年时就很难治疗，导致大量的瘫痪或者症状。

就是这个意思，说现代医学条件的改变并不一定就会带来对某些病症不良后果的有效防治。

[此贴子已经被作者于2008-5-27 2:36:18编辑过]

小小鱼儿04

太感谢各位大侠了，终于明白了第一题的选项