I have had mono for about two weeks. I don't feel that tired, but I have heard I cannot exercise. What can I do to stay in shape?

S.R.

It is often said that anyone who has infectious mononucleosis, or "mono," should not exercise. This advice stems from the fact that a rare but potentially life-threatening complication of mononucleosis is rupture of the spleen. The spleen is found in the upper left part of the abdomen. It is a blood-rich organ that plays an important role in the body's disease-fighting immune system. The spleen becomes enlarged during mono infection, so much so that the organ may burst open, resulting in a catastrophic loss of blood. Fortunately, rupture of the spleen is rare, occurring once in about 1,000 cases of mono.

In mono patients who have this complication, rupture is most likely to occur in the second or third week of illness. In about half the cases, the patient had recently suffered an injury to the abdomen. Therefore, it is generally recommended that people with mono avoid any contact sport and any other activity that could result in trauma to the spleen. I also advise that patients avoid weightlifting and sit-ups because of the strain they put on the abdominal muscles. I usually recommend brisk walking, because it is the least-stressful exercise to the abdomen, and because most mono patients do not feel like doing much more than that anyway.