Negative nucleic acid test for New Crown Virus is still needed after 6~7 days if there is travel to infected area or field and contact with suspected or confirmed infected person; negative nucleic acid test is not usually needed after 6~7 days if there is no travel to infected area or field, no contact with suspected or confirmed infected person and no need to travel to the field but it is necessary to take into account the local epidemic prevention policy. Nucleic acid testing involves the collection of secretions from the oral and nasal cavities of the human body to detect the presence of nucleic acid fragments of the new coronavirus. Nucleic acid testing is time-sensitive, with nucleic acid testing usually valid for about 48 hours in medium and high risk areas, and for 7 days in low risk areas. Therefore, even if the nucleic acid test is negative, it is necessary to re-test after 7 days to maximize the detection of the infected person and to prevent the spread of the virus. If you have not traveled to an infected area, come into contact with a suspected or confirmed infected person, or left the area within 7 days of a negative nucleic acid test, you usually do not need to take a new nucleic acid test. However, if public transportation is required to travel outside the area, a new nucleic acid test is required, as a negative nucleic acid test report within 48 hours is usually needed to travel outside the area.