It dropped dramatically in the period from 1954-- this is these filled black bars refer to this axis, polio cases per 100,000 population dropped down to only three or four cases by 1956.

患病率在一九五四年后的,一段时间里急剧下降,该坐标轴上的这些黑色柱形图表明,到一九五六年,小儿麻痹症的发病率,已经降低至每十万人中仅三到四人发病

耶鲁公开课 - 生物医学工程探索课程节选

They all died. And it was--not everybody, but in France 1,500,000 people died, and that's a huge demographic chunk, it's like a big shark took a big bite out of your basic pyramid of your demographic tree.

都死了,的确是,倒不是所有人,但是在法国有一百五十万人阵亡,这在人口比例中占很大一部分,就好像一个大鲨鱼照着,人口树的基底咬了一大口

耶鲁公开课 - 1871年后的法国课程节选