在过去二十年中，由于人群对疾病感染的免疫力下降、砍伐森林、城市化、人口流动和气候变化等因素的影响，黄热病病例数呈增加趋势。

The number of yellow fever cases has increased over the past two decades due to declining population immunity to infection, deforestation, urbanization, population movements and climate change.

youdao

纵观人口状况的这些变化特点，都与人口的迁移流动有着密切的关系。

It is noticed that all features of change in population conditions have a close relationship with population floating and migration.

youdao

但是，外来人口在职业流动中职业地位的变化并不大。

But, the change of ab extra population in status of the profession in professional flow is not big.

youdao