Infectious mononucleosis (also called mono) is a viral infection. It is a common infection, but often it does not cause any symptoms, especially when younger children have it. However, for adolescents and young adults it is a frequent cause of illness and missed school.
The virus that causes infectious mono is called the Epstein-Barr virus (EBV). It is spread mainly through saliva, which is why it has the nickname "kissing disease." Coughing, sneezing, or sharing drinking or eating utensils can also spread the virus.
Mono is most infectious from right before you start having symptoms until several days after your fever is gone.
After the virus enters the body it can take up to a month before symptoms begin. The first symptoms usually are:
Many people have extreme tiredness before they have any other symptoms. They may find that they are sleeping 12 to 16 hours a day.
After a few days of tiredness, fever, and aches, other symptoms are:
You may also have:
Your healthcare provider will ask about your symptoms and examine you. Your provider will look for fever; a red throat with swollen tonsils, sometimes covered with pus; and swollen lymph nodes in the neck. You may also have a red rash, especially on the chest, and an enlarged spleen (in the upper left abdomen).
A blood sample will be taken to test for mono. The first blood test might be negative. If your provider thinks you have mono, you may be asked to return in a few days for another blood test. If you have mono, this second test is usually positive.
You may also have a throat swab to check for strep throat.
There is no specific drug treatment for mono. Because it is a viral illness, antibiotics are not helpful. The most important thing you can do is to get plenty of rest.
Sometimes the mono infection causes the tonsils to become so big that they nearly block the throat. Your healthcare provider might prescribe steroid medicine to try to decrease the size of the tonsils. Using a steroid for a long time can have serious side effects. Take steroid medicine exactly as your healthcare provider prescribes. Don’t take more or less of it than prescribed by your provider and don’t take it longer than prescribed. Don’t stop taking a steroid without your provider's approval. You may have to lower your dosage slowly before stopping it.
Usually the fever, sore throat, and extreme tiredness last about 1 to 2 weeks. However, the tiredness can last for weeks or months. As you recover, you will be able to slowly go back to your normal activities.
An uncommon complication of mono is an abscess (pocket of infection) on 1 or both tonsils. The throat is very painful and swallowing is nearly impossible if you have a tonsil abscess. This infection needs to be treated with antibiotics. Sometimes the abscess needs to be opened by a surgeon.
Another uncommon, but dangerous complication is a ruptured spleen. Like the liver, the spleen can get enlarged during the infection. It can get so swollen that it actually bursts (ruptures). This is most likely to happen if you get hit in the belly, which is why you should not play sports until your healthcare provider says it’s okay. When your spleen ruptures, you may have sudden severe pain in the abdomen or you may feel like you are going to faint. If you have either of these symptoms, you need to call 911 right away.
With mono it can take several weeks, and in some cases several months, for the body's immune system to overcome the virus, but the illness is less contagious after the fever has been gone a few days.
The Epstein-Barr virus stays in the body even after you recover. You could have mono again, but this does not usually happen.
The best way to prevent others around you from getting mono is for them to avoid contact with your saliva. They should avoid kissing you and not share food, eating utensils, or drink containers with you until it has been several days since you stopped having a fever. The virus is less contagious at this time.
