How is mononucleosis transmitted?

A friend of mine has mono. As I understand it, the virus isn’t infectious until its later stages. She has had it for about two weeks now. Can I contract this while it’s still in its early stages simply through kissing? When does the disease become contagious?

Mononucleosis, or mono is caused by the Epstein-Barr virus (EBV). EBV is a member of the herpes virus family, and like all herpes viruses, once you are infected, the virus usually lives in your body for the rest of your life. In the case of EBV, about 90 percent of adults have been infected and are carrying the virus. Most of us get the illness in childhood, probably from our parents, since the virus is secreted into saliva and is easily transmitted through kissing. When a child gets mono, it may be relatively mild, and everyone simply assumes that it’s just a cold or flu. For this reason, most people don’t think they’ve ever had mono, but they have.

Adolescents and adults who never caught mono as kids typically get a severe illness with fever and fatigue that may last for several weeks. There is no antibiotic that is effective against the virus, but some doctors will treat severe cases with cortisone-type drugs to reduce the symptoms.

Doc’s Advice: How is mononucleosis transmitted?

Your friend was probably infectious from the moment she became ill, and she will shed virus in her saliva from time to time for the rest of her life. A previously infected person who is shedding virus doesn’t feel ill, and doesn’t know he or she is infectious, so there is no way to know when you shouldn’t kiss them. But since you have probably already had the disease yourself, there is no reason for you not to continue the relationship as soon as your friend feels well enough.

Because so many people have had mono as children, the disease does not sweep through dormitories or offices infecting people one after the other, the way the flu can. Instead, it is sporadic, infecting only those who missed it in childhood. If you and your friend had been kissing prior to her becoming ill, it may well have been you who gave it to her. Don’t feel guilty though; she would almost certainly have come in contact with the virus sooner or later.

EBV used to be considered the cause of chronic fatigue syndrome, but that connection has been pretty much debunked in recent years, and the cause of the syndrome remains unknown. EBV can cause some unusual kinds of malignancies, but generally only in people with severe immune deficiency.

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