Nucleic acid negativity at 7 days does not necessarily completely rule out the possibility of infection with a new crown. Especially when returning from a high-risk area, 2 weeks of observation and testing are generally required. If there is no history of exposure and several nucleic acid tests are completed within 7 days and the results are rendered negative, the possibility of infection can be largely ruled out. If there is a history of exposure and the amount of virus in the nucleic acid test specimen sampled from a nasal or throat swab is low, the nucleic acid result is positive or some external factor in the nucleic acid test process results in a false negative, therefore, neocollins cannot be completely ruled out. New crown virus is more insidious if the transmitted new crown virus is a mutated strain, such as Delta and Omicron. It is also possible that the infection with NeoCrown is just in its early stages and the nucleic acid test will not be positive. So a negative 7-day nucleic acid result does not completely rule out NeoCrown. In conclusion, a negative 7-day nucleic acid result cannot completely rule out new crowns, especially if there is a history of exposure or return from a high-risk area, and a 2-3 week observation period is needed.