人群规模大、流动性强，给防病知识普及带来非常大的难度。

The size of the crowd and mobile, to popularize knowledge about disease prevention very difficult.

youdao

人群规模大、流动性强，给防病知识普及带来非常大的难度。

The size of the crowd and mobile, to popularize knowledge about disease prevention very difficult.

youdao