The green sticker is to show that you have done nucleic acid testing, to reassure yourself and people around you, and to represent you in nucleic acid testing. Nucleic acid detection is a method to judge whether a patient is infected by virus by finding out whether there is DNA and RNA of invasive virus in respiratory tract samples, blood or feces, and it is the gold standard for diagnosing novel coronavirus infection.

After COVID-19 infects the human body, it will first reproduce in the respiratory system, so we can judge whether the human body is infected with the virus by detecting the virus nucleic acid in sputum and nasopharyngeal swab. The most commonly used method for detecting novel coronavirus-specific sequences is fluorescence quantitative PCR (polymerase chain reaction). Because the template of PCR reaction is only DNA, novel coronavirus nucleic acid (RNA) should be reverse transcribed into DNA before PCR reaction.