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Column originally published May 28, 2002

Teenager Can Be Sick For A Long Time With Mono

Question: Our teenage daughter recently came down with mono. She was very sick and was admitted to the hospital for one week. She couldn’t drink and required an IV. Her spleen was enlarged, and our doctor warned her about contact sports. She was tired for a long time and almost lost a whole semester of schooling. We are wondering whether she can get mono again in future. We are also concerned about our six-year-old son. Can he develop mono also?


It must have been a terrible ordeal for your family to go through your daughter’s illness. Infectious mononucleosis (IM), commonly called mono, is a serious condition that affects mostly teenagers and young adults. It is caused by the Epstein-Barr virus (EBV).

EBV is found all over the world. In North America, most children are infected within the first few years of life. At this age, the infection is not as serious, and it cannot be distinguished from any other bad cold. However, a small percentage of children will escape infection until they reach teenage years and young adulthood.

EBV infection is spread through the saliva. Once infected, a person will continuously excrete the virus in the saliva for the first 6 months. Afterwards, the virus is still excreted intermittently for the rest of the person’s life. At any given time, about 20-30 percent of people who have been infected with EBV will have the virus in their saliva. That is why it is so easy to catch the virus. Children can get EBV infection from their parents and other caretakers, as well as their playmates when they share their toys and saliva.

For the few teenagers and young adults who, by chance, did not pick up the virus at a younger age, EBV infection is often a long and painful illness. The virus is usually picked up from the saliva of another individual, through sharing of food or drink, as well as kissing (IM has been called the kissing disease). The incubation period (the time from infection until beginning of illness) is between 30 to 50 days.

EBV first infects the cells that cover the inside of the mouth, then spreads to the throat, and finally through the blood stream to the lymphatic tissue all over the body. When it enters the blood stream, symptoms of infectious mononucleosis begin.

The most common symptoms of IM are fatigue, fever, sore throat, and enlarged lymph nodes. The illness usually starts slowly, often takes one to two weeks before these teenagers come to medical attention. The fatigue is usually quite severe, many teenagers are not able to go to school or carry on their daily activities for weeks, sometimes even months. Fever can last for a few days to one or two weeks.

Almost everyone with mononucleosis have some enlargement of lymph nodes (also called lymph glands). Sometimes these glands can become very big, underneath the jaws and in the neck. This can raise concerns for other less common conditions like leukemia and lymphoma.

About half of the patients with IM will have enlargement of the spleen (this is called splenomegaly). The spleen is normally on the left side of abdomen, tugged under the rib cage for protection. When it is enlarged and engorged with blood, it extends below the rib cage where it is more prone to injury. Contact sports can lead to rupture of the spleen, which may require emergency surgery.

The sore throat in mononucleosis can be very severe so that swallowing is difficult, and IV is required to prevent or treat dehydration. The tonsils are often markedly enlarged, with white patches on them. It is sometimes difficult to distinguish, based on examination alone, whether a person has mononucleosis or Strept throat.

Strept throat, due to Group A Streptococcal infection, requires penicillin type of antibiotic for treatment. However, if ampicillin or amoxicillin (both are related to penicillin) is given to those with mononucleosis, about 80% of them will develop a rash. This complication can be confused as penicillin allergy.

Rarely, these enlarged tonsils can affect breathing and swallowing. When this happens, a short course of steroids is needed to reduce reaction of the lymphatic tissue to EBV, thereby shrinking the size of the tonsils. However, steroids are not used to reduce enlarged lymph nodes or spleen.

At the present time, there is no medicine that can effectively fight EBV infection. Fortunately, almost all infectious mononucleosis will resolve with time. Lethargy may last for months, but sooner or later, the person will recover. There are cases of cancer, especially in southern Chinese, which are caused by EBV, but I will not discuss this any further here.

EBV infection induces life-long immunity. Once a person is infected, either as a young child or in teenage years, there is no opportunity for a second infection. Therefore, you don’t have to worry about your daughter developing mono again.

As for your son, there is a fairly good chance that he might have already been infected with EBV that you didn’t recognize. If he didn’t, he can pick up the virus from his older sister. However, the chance is that he will not be as sick as her. One thing I should caution here, the ‘Monospot test’ that is used for diagnosis of infectious mononucleosis in teenagers and adults are often negative in young children. If confirmation is necessary, it is important to use specific EBV antibody tests.

I hope the above information is useful to reduce some of your worries about your children.