Most EBV infections are not severe, and clinically, almost all adults tested positive for antibodies to EBV, IgG, the nuclear antigen of EBV, and IgG, the capsid antigen, meaning that they have been infected in the past. The fact that previous infections have not been diagnosed before and there is no particular discomfort means that the infection was probably asymptomatic at the time of infection or only manifested itself as a common cold or fever. So most people infected with EBV will not have serious manifestations. However, clinically, serious infections related to EBV infection can be found, such as infectious mononucleosis, in which the patient has a marked elevation of monocytes, accompanied by enlargement of lymph nodes, tonsils, and even spleen, as well as a skin rash. In the case of EBV infection, resulting in hemophagocytic syndrome, it is a more serious manifestation. While most are mild, some are more severe.