What happened when the green code suddenly turned yellow?

The code that suddenly turns yellow is that you have been to a high-risk area or have had contact with close contacts. If neither of these situations exists, then most of the reasons are caused by space-time phenomena.

For example, 14 days, you have been to the same place as the confirmed patient. Although there is no physical contact, due to the drift of communication signals, the system detects that you and the diagnosed patient are accompanied by time and space, so you are defined as a time and space companion in the risk group, and the health code may turn yellow.

Definition and processing method of spatio-temporal adjoint

Spatio-temporal companionship refers to being with the diagnosed patient in the same spatio-temporal grid (usually 800 m * 800 m as the detection range) 14 days.

I suggest you report to the local community units as soon as possible and obey the local epidemic prevention requirements and arrangements. On the premise of strict 14-day self-health monitoring and personal protection, go to the local designated nucleic acid testing place for nucleic acid testing.