Nucleic acid test CT value >40 is negative and is usually an indicator of a novel coronavirus nucleic acid test.A higher CT value means that the virus is more difficult to find, indicating that the amount of virus in the extracted sample is low. Nucleic acid test value is mainly through the fluorescence quantitative PCR technology to reflect the amount of virus inside the human body. If the nucleic acid test value is smaller, then it means that the number of PCR amplification cycles is less, which means that the virus concentration is higher and can be easily detected. On the other hand, if the value is high, it means that the amount of virus in the body is low and needs to be amplified several times before it can be detected. Generally speaking, a nucleic acid test value of <37 is positive, and between 37 and 40 is a gray area that needs to be repeated. And if the value >40, then it means the result is negative. However, it is important to note that the size of the nucleic acid test value alone does not confirm the diagnosis of the disease, but also needs to be combined with the nucleic acid test as well as specific clinical symptoms to make a comprehensive judgment, such as fever, cough and sore throat.