If the train only passes through the high-incidence area, there is no epidemic at the origin, destination and carriage, so there is no need for isolation. Generally, nucleic acid testing is required when going out and returning to the province. As long as the nucleic acid testing is negative, there is no need for isolation. If you stay in an epidemic area, you must do nucleic acid testing and self-isolation after returning home. When the health code turns orange, it will affect your travel, but you can't walk in most public areas, such as buses, subways, shopping malls and other crowded places. In short, it is best not to go out. It is suggested to implement self-isolation measures for 7 days or 14 days or to do nucleic acid detection twice. The interval between the two tests was more than 72 hours, and the results were negative. The system cancels the yellow code or orange code and uses the green code instead.