Infectious mononucleosis

Infectious mononucleosis (IM, mono), also known as glandular fever, is an infection usually caused by the Epstein–Barr virus (EBV). Most people are infected by the virus as children, when the disease produces few or no symptoms. In young adults, the disease often results in fever, sore throat, enlarged lymph nodes in the neck, and fatigue. Most people recover in two to four weeks; however, fatigue may last months. The liver or spleen may also become swollen, and in less than one percent of cases splenic rupture may occur. While usually caused by the Epstein–Barr virus, also known as human herpesvirus 4, which is a member of the herpesvirus family, a few other viruses and the protozoon Toxoplasma gondii may also cause the disease. It is primarily spread through saliva but can rarely be spread through semen or blood. Spread may occur by objects such as drinking glasses or toothbrushes, or through a cough or sneeze. Those who are infected can spread the disease weeks before symptoms develop. Mono is primarily diagnosed based on the symptoms and can be confirmed with blood tests for specific antibodies. Another typical finding is increased blood lymphocytes of which more than 10% are reactive. The monospot test is not recommended for general use due to poor accuracy. There is no vaccine for EBV; however, there is ongoing research. Infection can be prevented by not sharing personal items or saliva with an infected person. Mono generally improves without any specific treatment. Symptoms may be reduced by drinking enough fluids, getting sufficient rest, and taking pain medications such as paracetamol (acetaminophen) and ibuprofen. Mononucleosis most commonly affects those between the ages of 15 and 24 years in the developed world. In the developing world, people are more often infected in early childhood when there are fewer symptoms. In those between 16 and 20 it is the cause of about 8% of sore throats. About 45 out of 100,000 people develop infectious mono each year in the United States. Nearly 95% of people have had an EBV infection by the time they are adults. The disease occurs equally at all times of the year. Mononucleosis was first described in the 1920s and is colloquially known as "the kissing disease".

Signs and symptoms

The signs and symptoms of infectious mononucleosis vary with age.

Children Before puberty, the disease typically only produces flu-like symptoms, if any at all. When found, symptoms tend to be similar to those of common throat infections (mild pharyngitis, with or without tonsillitis).

Adolescents and young adults In adolescence and young adulthood, the disease presents with a characteristic triad:

Fever – usually lasting 14 days; often mild. Sore throat – usually severe for 3–5 days, before resolving in the next 7–10 days. Swollen glands – mobile; usually located around the back of the neck (posterior cervical lymph nodes) and sometimes throughout the body. Another major symptom is feeling tired. Headaches are common, and abdominal pains with nausea or vomiting sometimes also occur. Symptoms most often disappear after about 2–4 weeks. However, fatigue and a general feeling of being unwell (malaise) may sometimes last for months. Fatigue lasts more than one month in an estimated 28% of cases. Mild fever, swollen neck glands and body aches may also persist beyond 4 weeks. Most people can resume their usual activities within 2–3 months. The most prominent sign of the disease is often pharyngitis, which is frequently accompanied by enlarged tonsils with pus—an exudate similar to that seen in cases of strep throat. In about 50% of cases, small reddish-purple spots called petechiae can be seen on the roof of the mouth. Palatal enanthem can also occur, but is relatively uncommon. A small minority of people spontaneously present a rash, usually on the arms or trunk, which can be macular (morbilliform) or papular. Almost all people given amoxicillin or ampicillin eventually develop a generalized, itchy maculopapular rash, which however does not imply that the person will have adverse reactions to penicillins again in the future. Occasional cases of erythema nodosum and erythema multiforme have been reported. Seizures may also occasionally occur.

Complications Spleen enlargement is common in the second and third weeks, although this may not be apparent on physical examination. Rarely, the spleen may rupture. There may also be some enlargement of the liver. Jaundice or EBV-induced hepatitis occurs only occasionally. It generally gets better on its own in people who are otherwise healthy. When caused by EBV, infectious mononucleosis is classified as one of the Epstein–Barr virus–associated lymphoproliferative diseases. Occasionally, the disease may persist and result in a chronic infection. This may develop into systemic EBV-positive T cell lymphoma.

Older adults Infectious mononucleosis mainly affects younger adults. When older adults do catch the disease, they less often have characteristic signs and symptoms such as the sore throat and lymphadenopathy. Instead, they may primarily experience prolonged fever, fatigue, malaise, and body pains. They are more likely to have liver enlargement and jaundice. People over 40 years of age are more likely to develop serious illness.

Incubation period The exact length of time between infection and symptoms is unclear. A review of the literature made an estimate of 33–49 days. In adolescents and young adults, symptoms are thought to appear around 4–6 weeks after initial infection. Onset is often gradual, though it can be abrupt. The main symptoms may be preceded by 1–2 weeks of fatigue, feeling unwell and body aches.

Cause

Epstein–Barr virus

About 90% of cases of infectious mononucleosis are caused by the Epstein–Barr virus, a member of the Herpesviridae family of DNA viruses. It is one of the most commonly found viruses throughout the world. Contrary to common belief, the Epstein–Barr virus is not highly contagious. It can only be contracted through direct contact with an infected person's saliva, such as through kissing or sharing toothbrushes. About 95% of the population has been exposed to this virus by the age of 40, but only 15–20% of teenagers and about 40% of exposed adults develop infectious mononucleosis.

Cytomegalovirus

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