After a virus infects the human body, the vast majority of cases are cleared without any clinical symptoms, and the corresponding immunity is obtained, so in adults, cytomegalovirus antibodies, EBV antibodies and IgG antibodies to hepatitis A virus can be found in the vast majority of previous infections, and these antibodies will be positive. The majority of these antibodies will be positive, so it is the vast majority of cases. For example, influenza virus infection can cause fever, sneezing, runny nose, cough, sputum, sore throat, and other systemic symptoms such as fever and respiratory symptoms mainly in the upper respiratory tract. In the case of varicella virus infection, the initial infection will cause fever and a generalized rash, while in the case of reinfection, it will only cause a rash in the area innervated by the nerves. Infections like hepatitis virus may cause abnormal liver function and jaundice. Therefore, the symptoms after a virus infection in the body should be judged according to the specific type of virus and whether it is a primary or secondary infection.