A clinical case of a combined course of Epstein-Barr viral infection and mumps in a 20-year-old man is presented. The combination of clinical symptoms characteristic of Epstein-Barr viral infection and hypersalivation, followed by an increase in α-amylase in the blood, which developed a few days after hospitalization, caused the extension of the diagnostic search in order to clarify the diagnosis. Diagnostic errors and difficulties encountered in the management of patients with upper respiratory tract lesions were noted.Funding. The study had no sponsor support. Conflict of interest. The authors declare no conflict of interest.