What Happens

Usually mono is a mild illness that goes away without treatment after several weeks. When you have mono, your symptoms may come and go, and your symptoms may change with time.¹

• A sore throat is worst during the first 3 to 5 days and gradually improves over the next 7 to 10 days.
• Fever may last 10 to 14 days. Usually it is mild during the last 5 to 7 days. If you have a fever, you should stay home from work or school until the fever goes away. You can then go back to your normal activities if you feel up to it.
• Swollen lymph nodes (sometimes called swollen glands) may last up to 4 weeks.
• It may take several weeks (even months) for your energy level to return to normal. Don't try to rush this process. Pushing yourself too hard could make you feel worse. Give your body the rest it needs.

Mono can cause your spleen to enlarge, making it prone to injury. To reduce the risk of injuring your spleen, avoid heavy lifting and contact sports for 4 weeks after you become ill with mono (or until a doctor tells you it is okay).

If you know you have mono, you should not donate blood. Epstein-Barr virus (EBV) can be spread through blood products, although this is not common.

Complications of mono are rare but are most likely to develop in very young children, older adults who are in poor health, and people who have impaired immune systems.

In the past, both infectious mononucleosis and chronic fatigue syndrome were thought to be caused by the Epstein-Barr virus. But it is now believed that even though both conditions have some similar symptoms, they are different diseases and chronic fatigue syndrome is not caused by the Epstein-Barr virus.