If you haven't been to the disease risk area, what should I do if Tianjin suddenly turns from a green code to a yellow code?

There are several reasons:

First, I passed through the epidemic area, or stayed near the epidemic area, resulting in yellow code;

Second, the complainant is still under health observation, please wait patiently;

Third, the complainant's own information was used or stolen by others, and the related behavior of others led to the complainant being sentenced to a yellow code.