Normal lung CT can rule out novel coronavirus pneumonia, but it cannot rule out neocoronavirus infection, because novel coronavirus infection manifests itself in some people as asymptomatic infected people, some people have only upper respiratory tract symptoms, while some people may have manifestations of pneumonia. Mild cases have mild symptoms and may present with cough, malaise, sore throat, low-grade fever, and diarrhea, but there is no pneumonia, so lung imaging is normal, but they are also contagious, and the diagnosis can be confirmed by a nucleic acid test for coronavirus. A positive nucleic acid test is also a confirmed case of novel coronavirus. Diagnosis of mild cases of novel coronavirus pneumonia, or asymptomatic infections, is often difficult and is made through epidemiologic testing, blood tests, CRP, and other relevant tests. The diagnosis of novel coronavirus pneumonia is still primarily made by nucleic acid testing, or serologic antibodies to the virus.