Mononucleosis, also called mono or the kissing disease, is an infection caused by the Epstein-Barr virus. It’s most common in teens and young adults. It usually goes away on its own without causing serious illness.
The early symptoms of mononucleosis are like those of the flu. You might have:
- Severe fatigue
- A headache
- A sore throat, which can be severe
- Chills followed by a fever
- Muscle aches
After a day or two, you may also have:
- Swollen lymph nodes and tonsils
- A measles-like rash on your face or body. It might begin suddenly after you’ve taken amoxicillin for a severe sore throat.
- Tiny red spots or bruise-like areas inside your mouth, especially on the roof of your mouth (palate)
- Soreness in your upper left belly because of an enlarged spleen
How Long Do Symptoms Last?
Signs of mono usually show up 4 to 6 weeks after you’re infected with the virus. Most people feel better after 2 to 4 weeks, but they may be tired for several weeks after that. Symptoms can sometimes last 6 months or more.
When to Call Your Doctor
Talk to your doctor if:
- You have mono symptoms for longer than 10 days or you have a severe sore throat for more than a day or two. Your doctor will want to rule out other illnesses, such as strep throat.
- You have a severe headache that won’t go away and a stiff neck, which might be signs of meningitis
- You get a rash of many tiny red spots (petechiae), which could be a sign of a lack of platelets in your blood or another serious illness such as meningitis
- You have yellow skin or eyes (jaundice), which may be a sign of hepatitis
- You have signs of other illnesses including swollen lymph nodes all over your body, trouble breathing, a long-lasting fever over 101.5 F, or weakness in your arms and legs