If you go to a low-risk area, the health code will not change color when you return to the local area. If the place you go to suddenly becomes a medium-high risk area after you come back, then the relevant personnel will call you to be isolated and ask you to cooperate with the current situation. During the epidemic, everyone should make all kinds of preparations before leaving. Two "identical" nucleic acid positive cases will become "yellow code". Relevant departments will assist in epidemic prevention and control through big data analysis according to the national epidemic situation. If you have been in a key epidemic area, such as a confirmed case or an asymptomatic infected person, and you happen to have activities near the same area at the same time, it means that you have been included in the health screening management. If you: return from the city where the domestic high-risk areas are located; When you return from a city with a moderate risk of local transmission, the health code will become a "yellow code".