Infectious Mononucleosis: Understanding the Symptoms and Precautions Infected with mononucleosis? Here’s what you need to know about the symptoms and how to manage them. Symptoms Fever: Individuals typically experience a persistent high fever, with temperatures reaching up to 39-40°C. This fever tends to be more pronounced in the evenings or at night and can last for several days to weeks. Chills and sweating are common during these periods, and severe fever can even affect sleep quality. National Center for Biotechnology Information Sore Throat: This is one of the characteristic symptoms, manifesting as severe pain in the throat, particularly when swallowing.... Learn more