Frequently, patients present with fever, sore throat, and swollen lymph nodes, which are ineffectively treated with repeated antibiotics. Later, they come to our Infectious Diseases Department and are diagnosed with infectious mononucleosis after examination. What is infectious mononucleosis? This is an infectious disease caused by EBV infection. Its clinical manifestations may include fever, sore throat, swollen lymph nodes, and in some cases, an enlarged liver and spleen and a skin rash. Because it is a viral infection, antibiotic therapy is not effective. Therefore, patients with persistent high fever, swollen lymph nodes, sore throat and other symptoms that are not treated with antibiotics should be highly suspected of this disease. In addition, the ancillary tests for this disease are also specific. Blood tests usually show an increased ratio of lymphocytes to monocytes, and the total number of white blood cells can be normal, decreased or increased. Blood EBV antibody IgM is positive and blood EBV DNA is positive. Treatment is mainly symptomatic, i.e., antipyretic, rehydration, and relief of pharyngeal and lymph node pain are the main treatments. Antiviral treatment has no clear effect. If the symptoms are severe, glucocorticoids can be applied under medical supervision to relieve the symptoms. The disease is self-limiting and can be cured within 1-3 weeks. However, some patients may have the disease for up to 6 months.