Infectious mononucleosis – Health Web

Infectious mononucleosis, (also known as the kissing disease, or Pfeiffer’s disease, in North America as mono, and more commonly known as glandular fever in other English-speaking countries), is a disease seen most commonly in adolescents and young adults, characterized in teenagers by fever, sore throat, muscle soreness, and fatigue. Mononucleosis typically produces a very mild illness in small children. White patches on the tonsils or in the back of the throat may also be seen, (resembling strep throat). Mononucleosis is usually caused by the Epstein-Barr virus (EBV), which infects B cells (B-lymphocytes), producing a reactive lymphocytosis and atypical T cells (T-lymphocytes) known as Downey bodies.

Mononucleosis is typically transmitted from asymptomatic individuals through blood or saliva (hence “the kissing disease”), or by sharing a drink, or sharing eating utensils. The disease is far less contagious than is commonly thought. In rare cases a person may have a high resistance to infection. The disease is so-named because the count of mononuclear leukocytes (white blood cells with a one-lobed nucleus) rises significantly. There are two main types of mononuclear leukocytes: monocytes and lymphocytes. They normally account for about 35% of all white blood cells. With infectious mononucleosis, this can rise to 50-70%. Also, the total white blood count may increase to 10000-20000 per cubic millimeter.


Symptoms usually appear 1-2 months after infection, and may resemble strep throat, or other bacterial or viral respiratory infections. The typical symptoms and signs of mononucleosis are:

  • Fever – this varies from mild to severe, but is seen in nearly all cases.
  • Enlarged and tender lymph nodes – particularly the posterior cervical lymph nodes, on both sides of the neck.
  • Sore throat** White patches on the tonsils and back of the throat are often seen.
  • Fatigue (sometimes extreme fatigue).

Some patients also display:

  • Enlarged spleen (splenomegaly, which may lead to rupture) and/or liver (hepatomegaly).
  • Petechial hemorrhage.
  • Abdominal pain.
  • Aching muscles.
  • Headache.
  • Loss of appetite.
  • Jaundice.
  • Depression.
  • Weakness.
  • Skin rash.
  • Dizziness or disorientation.
  • Dry cough.
  • Enlarged Prostate.
  • Inflamed genitals.
  • Supra-orbital oedema (the eyes become puffy and swollen) may occur in the early stages of infection.

After an initial prodrome of 1-2 weeks, the fatigue of infectious mononucleosis often lasts from 1-2 months. The virus can remain dormant in the B cells indefinitely after symptoms have disappeared, and resurface at a later date. Many people exposed to the Epstein-Barr virus do not show symptoms of the disease, but carry the virus and can transmit it to others. This is especially true in children, in whom infection seldom causes more than a very mild illness which often goes undiagnosed. This feature, along with mono’s long (4 to 6 week) incubation period, makes epidemiological control of the disease impractical. About 6% of people who have had infectious mononucleosis will relapse.

Mononucleosis can cause the Spleen to swell. Rupture may occur without trauma, but impact to the spleen is also a factor. Other complications include hepatitis (inflammation of the liver) causing elevation of serum bilirubin (in approximately 40% of patients), jaundice (approximately 5% of cases), and anemia (a deficiency of red blood cells). In rare cases, death may result from severe hepatitis or splenic rupture.

Reports of splenomegaly (enlarged spleen) in infectious mononucleosis suggest variable prevalence rates of 25% to 75%. Among pediatric patients, a splenomegaly rate of 50% is expected, with a rate of 60% reported in one case series. Although splenic rupture is a rare complication of infectious mononucleosis, it is the basis of advice to avoid contact sports for 4-6 weeks after diagnosis.

Usually, the longer the infected person experiences the symptoms the more the infection weakens the person’s immune system and the longer he/she will need to recover. Cyclical reactivation of the virus, although rare in healthy people, is often a sign of immunological abnormalities in the small subset of organic disease patients in which the virus is active or reactivated.

Although the great majority of cases of mononucleosis are caused by the E.B. virus, cytomegalovirus can produce a similar illness, usually with less throat pain. Due to the presence of the atypical lymphocytes on the blood smear in both conditions, most clinicians include both infections under the diagnosis of “mononucleosis.” Symptoms similar to those of mononucleosis can be caused by adenovirus, acute HIV infection and the protozoan Toxoplasma gondii.


Infectious mononucleosis is generally self-limiting and only symptomatic and/or supportive treatments are used. Rest is recommended during the acute phase of the infection, but activity should be resumed once acute symptoms have resolved. Nevertheless heavy physical activity and contact sports should be avoided to abrogate the risk of splenic rupture, for at least one month following initial infection and until splenomegaly has resolved, as determined by ultrasound scan. The patient should avoid eating excessively sweet things for a few months.

In terms of pharmacotherapies, acetaminophen/paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) may be used to reduce fever and pain – aspirin is not used due to the risk of Reye’s syndrome in children and young adults. Intravenous corticosteroids, usually hydrocortisone or dexamethasone, are not recommended for routine use but may be useful if there is a risk of airway obstruction, severe thrombocytopenia, or hemolytic anemia.

There is little evidence to support the use of aciclovir, although it may reduce initial viral shedding. Antibiotics are not used, being ineffective against viral infections, with amoxicillin and ampicillin contraindicated (for other infections) during mononucleosis as their use can frequently precipitate a non-allergic rash. In a small percentage of cases, mononucleosis infection is complicated by co-infection with streptococcal infection in the throat and tonsils (strep throat). Penicillin or other antibiotics should be administered to treat the strep throat, but are not effective against EBV. Opioid analgesics are also contraindicated due to risk of respiratory depression.