Why does Shangqiu turn yellow in Zhengzhou?

According to relevant information, Shangqiu turned yellow to Zhengzhou because people who came back from outside the province (entered Zhengzhou). According to the Measures for Health Management of People Returning to Henan Province by the Office of Henan Provincial Epidemic Prevention and Control Headquarters and the requirements of relevant epidemic prevention and control measures in Zhengzhou City, the people returning to Henan Province (entering Zheng) are given a yellow code, and corresponding epidemic prevention and control measures such as three-day two inspections, health monitoring and medical observation are implemented according to their residence history within 14 days.