Infectious mononucleosis

Infectious mononucleosis, often called "mono" or glandular fever, is a contagious infection.

It is most commonly caused by the Epstein–Barr virus (EBV), a member of the herpesvirus family. While EBV causes about 90% of cases, other agents can trigger the disease. These include the cytomegalovirus (CMV), which causes 5% to 7% of cases, and the protozoon Toxoplasma gondii, which causes less than 1% of cases. Other rare causes include adenovirus, rubella, and herpes simplex viruses. Understanding mono is vital because nearly 95% of the population is exposed to EBV by age 40.

The biological mechanism of the infection follows a specific sequence. The virus first replicates within the epithelial cells of the pharynx, the tissue in the throat.

This initial replication often leads to pharyngitis, which is a painful sore throat. After this stage, the virus moves to invade B cells, which are a type of white blood cell. The body responds with an immune defense involving cytotoxic T cells. These T cells target the infected B lymphocytes. This interaction results in the creation of enlarged, reactive lymphocytes, also known as Downey cells.

This cellular battle is a primary driver of the symptoms patients experience.

Symptoms of the disease vary significantly depending on a person's age. In children, the illness is often mild and may only produce flu-like symptoms or minor throat infections. Adolescents and young adults typically experience a characteristic triad of symptoms. This includes a fever that usually lasts 14 days, a severe sore throat for 3 to 5 days, and swollen lymph nodes. These swollen glands are often mobile and located around the back of the neck. Young adults also frequently suffer from intense fatigue, headaches, and abdominal pain.

In older adults, the presentation of the disease changes again. They are less likely to experience the classic sore throat or swollen glands. Instead, they often face prolonged fever, fatigue, and body pains. Older adults are also more prone to liver enlargement and jaundice, which is a yellowing of the skin or eyes. People over the age of 40 are more likely to develop a serious illness from the infection. While most people recover within two to four weeks, fatigue can persist for months in about 28% of cases.

Medical history shows that infectious mononucleosis was first described in the 1920s. It earned the nickname "the kissing disease" because it is primarily spread through saliva.

Transmission can occur through kissing, sharing drinking glasses, or using shared toothbrushes. It can also spread through coughing or sneezing. Interestingly, an infected person can spread the virus weeks before they even feel sick. The incubation period, or the time between infection and symptoms, is estimated to be between 33 and 49 days. Some studies suggest people may remain contagious for up to 18 months.

Diagnosis relies on physical exams and specific laboratory tests. Doctors look for swollen lymph nodes and an enlarged spleen to suspect the illness. They may also check for petechiae, which are small reddish-purple spots on the roof of the mouth.

The monospot test, or heterophile antibody test, is one method used, but it has poor accuracy. Because of this, the CDC does not recommend it for general use. Instead, doctors often use serology to detect specific antibodies. They look for Immunoglobulin M (IgM) to identify current infections and Immunoglobulin G (IgG) to identify past infections.

There are several notable complications and side effects to consider. In about 50% of cases, patients may see petechiae in the mouth. A common complication is splenomegaly, which is the enlargement of the spleen.

In less than 1% of cases, the spleen may actually rupture. Some patients may also develop a rash if they take certain medications like amoxicillin while infected. Furthermore, the disease can occasionally lead to secondary cold agglutinin disease, an autoimmune condition affecting red blood cells. In very rare instances, the infection can become chronic and lead to T cell lymphoma.

Managing mono focuses on supporting the body while it fights the virus. There is currently no vaccine for EBV, though research is ongoing. Most cases improve without specific medical treatment. Patients are encouraged to drink plenty of fluids and get sufficient rest. Pain medications like paracetamol or ibuprofen can help reduce discomfort. By avoiding the sharing of personal items, people can help prevent the spread of this common virus.