infectious mononucleosis

infectious mononucleosis

mononucleosis, infectious, acute infectious disease of older children and young adults, occurring sporadically or in epidemic form, also known as mono, glandular fever, and kissing disease. The causative organism is a herpesvirus known as Epstein-Barr virus. The disease occurs most often in patients between the ages of 15 and 35. The virus is present in the saliva; it is usually spread by sharing a glass or kissing. Symptoms usually take 30 to 50 days to develop.

Diagnosis of mononucleosis follows the exhibition of a large number of abnormal white blood cells (lymphocytes) on microscopic blood examination. These blood cells have a single nucleus that give the disease its name. Symptoms are varied but include enlarged lymph nodes, sore throat, fever, enlarged spleen in about half the cases, and excessive fatigue. Occasional rashes and throat and mouth infections occur. Liver inflammation is common. Fatalities are very rare and, when they do occur, usually result from splenic rupture. General therapeutic measures include bed rest and treatment of symptoms.

Infectious mononucleosis, also known as Pfeiffer's disease, mono (in the United States of America) and more commonly known as glandular fever in other English-speaking countries, is an infectious disease. It occurs most commonly in adolescents and young adults, where it is characterized by fever, sore throat, muscle soreness, and fatigue. Infectious mononucleosis typically produces a mild illness and is often asymptomatic. Mononucleosis is predominantly caused by the Epstein-Barr virus (EBV), which infects B cells (B-lymphocytes), producing a reactive lymphocytosis predominantly consisting of atypical lymphocytes, a specific type of T-cell that gives the disease its name.

The name "kissing disease" is often applied to mono in casual speech, as in developed countries it is most common at the same age when adolescents and young adults are initiating romantic behaviour. This co-occurrence is not apparent in undeveloped countries, where poor sanitation and close living arrangements cause the causative virus to be spread at a much earlier age, when the disease is mild and seldom diagnosed. Both males and females are susceptible to mononucleosis.


Additional symptoms include:

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. This is especially true in children, in whom infection seldom causes more than a very mild cold which often goes undiagnosed. Children are typically just carriers of the disease. 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.

Although most cases of mononucleosis are caused by the E.B. virus, the condition is defined by the clinical presentation and laboratory findings. Cytomegalovirus can produce a similar illness, usually with less throat pain, and also generate atypical lymphocyte proliferation. In recent years, as precise virological and serological studies are more commonly done to identify the actual causative virus, some clinicians have taken to use "mononucleosis" to refer only to the E.B. virus cases. Symptoms similar to those of mononucleosis can also be caused by adenovirus, acute HIV infection and the protozoan ''Toxoplasma gondii


Laboratory findings usually include an elevated white blood cell count and abnormal liver function tests. The white cell count elevation is predominantly in the lymphocyte portion, and of those the majority is often of the atypical form characteristic of the disease.

Specific tests for EBV include:


Mononucleosis is typically transmitted from asymptomatic individuals through saliva, earning it the name "the kissing disease", or by sharing a drink, or sharing eating utensils. As with many viral infections, such as chickenpox, antibodies are developed by individuals who become infected with the disease and recover. In most individuals, these antibodies remain in their system, creating lifelong immunity to further infections.

Atypical presentations of mononucleosis/EBV infection

In small children, the course of the disease is frequently asymptomatic. Some adult patients suffer fever, tiredness, lassitude (abnormal fatigue), depression, lethargy, and chronic lymph node swelling, for months or years. This variant of mononucleosis has been referred to as chronic EBV syndrome or chronic fatigue syndrome (CFS), although CFS is a distinct condition from IM. Still, current studies suggest there is an association between infectious mononucleosis and CFS. In case of a weakening of the immune system, a reactivation of the Epstein-Barr virus is possible; in CFS there is evidence of immune activation also. "Chronic fatigue states" as defined by the CDC criteria for CFS, appear to occur in 10% of those who contract mononucleosis. Chronic fatigue may then be a rather common side effect of infectious mononucleosis. On the other hand, studies conducted by the CDC and others have discounted a link between EBV and CFS.

Perhaps a majority of chronic post infectious "fatigue states" appear not to be caused by a chronic viral infection, but are triggered by the acute infection. Direct and indirect evidence of persistent viral infection has been found in CFS, for example in muscle and via detection of an unusually low molecular weight RNase L enzyme, although the commonality and significance of such findings is disputed. Hickie et al contend that mononucleosis appears to cause a hit and run injury to the brain in the early stages of the acute phase, thereby causing the chronic fatigue state. This would explain why in mononucleosis, fatigue very often lingers for months after the Epstein Barr virus has been controlled by the immune system. Just how infectious mononucleosis changes the brain and causes fatigue (or lack thereof) in certain individuals remains to be seen. Such a mechanism may include activation of microglia in the brain of some individuals during the acute infection. Microglia may remain activated or "damaged" for months following infection, thereby causing a slowly dissipating fatigue. Secondary infections can occur. Such infections include mild swelling of the cartilage between the sternum and ribs occurring approximately one month after initial diagnosis.


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.

In terms of pharmacotherapies, acetaminophen/paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) may be used to reduce fever and pain.

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. However, the antiviral drug valacyclovir has recently been shown to lower or eliminate the presence of the Epstein-Barr virus in subjects afflicted with acute mononucleosis, leading to a significant decrease in the severity of symptoms. Antibiotics are not used as they are ineffective against viral infections. The antibiotics amoxicillin and ampicillin are relatively contraindicated in the case of any coinciding bacterial infections during mononucleosis because 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 (with the exception of the two mentioned above) should be administered to treat the strep throat. Opioid analgesics are also relatively contraindicated due to risk of respiratory depression.

Morbidity and mortality

Fatalities from mononucleosis are nearly impossible in developed nations. Uncommon, nonfatal complications exist, including various forms of CNS and hematological affection:


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