If a case of polio emerged in the community, the chances that it could spread to other children or to your child were high; so, great interest in this in the early part of this century.
如果在某个社区出现一例脊髓灰质炎患儿,那么你的孩子或者更多别的孩子,被传染的几率非常高,所以 二十世纪初的科学家们,热衷于研究脊髓灰质炎
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