Nasopharyngeal cancer is not necessarily positive for EBV, and the occurrence of nasopharyngeal cancer is very closely related to EBV infection. At present, there are two main methods to detect EBV, as follows: First, detection of EBV antibodies in the serum: the most commonly used is the detection of VCA-IgA and EA-IgA. Almost 100% of patients with non-keratinizing nasopharyngeal carcinoma have anti-EBV antibodies inside the serum. The positivity rate of these antibodies in nasopharyngeal carcinoma, according to the literature, is about 69%-93%, so it is not 100%. Second, detection of plasma EBV free DNA: Because EBV DNA molecule is a good marker for nasopharyngeal cancer, it can be widely used in various aspects of nasopharyngeal cancer, such as early diagnosis, prognosis, monitoring of efficacy, and clinical staging. The sensitivity can reach 96%, but not 100%, so it is not necessarily positive for EBV in nasopharyngeal cancer.