Nucleic acid testing currently refers mostly to the new coronavirus nucleic acid test, and showing 7d negative generally means that a nucleic acid test within the last 7 days was negative. 7d (7 days) means 7 days, if the last negative nucleic acid test is 7 days from the present or multiple negative nucleic acid test results in the last 7 days, then the health code will show 7d negative. However, showing a negative nucleic acid result within 7 days does not necessarily mean that it is safe, nor does it mean that it is not necessarily infected with the new coronavirus. At present, the new coronavirus is highly contagious, and there exists a certain period of time of incubation after infection, and many patients appear positive only after multiple nucleic acid tests. Therefore, individuals need to do their own protection, do not gather, do not bunch up, according to the state, community and unit requirements for routine nucleic acid testing.