As for the "health code", no matter in low-risk or medium-high-risk areas, you must hold a "green code" when taking the high-speed rail. In principle, "yellow code" and "red code" are not allowed to take the high-speed rail.
Validity period of sitting high-iron nucleic acid detection
The validity period of general nucleic acid testing is one week. The result of nucleic acid test is negative, which only shows that the possibility of novel coronavirus infection is temporarily ruled out at this time. However, there is still a time limit for the test results. Generally speaking, the test results within 7 days can be used as a reference, which is why the nucleic acid test should be carried out within one week after returning to school.
The validity period of nucleic acid detection should consider the incubation period of virus infection. At present, most of these viruses develop within 14 days. For safety reasons, nucleic acid testing should be carried out within 7 days.