Infectious mononucleosis

Introduction

Infectious mononucleosis, an acute viral infection, mainly results from the Epstein-Barr virus (EBV) which belongs to the Herpes virus family, accounting for 90% of cases. Other viruses like cytomegalovirus, human Herpes virus 6, human immunodeficiency virus, and adenoviruses can also cause it, making up the remaining percentage. These viruses have a widespread global presence, infecting 90-95% of the population. The term "infectious mononucleosis" originated in 1920 during a study on a group of students who exhibited symptoms such as pharyngitis, lymphocytosis, and atypical mononuclear cells. Only humans spread this disease.

EBV Transmission

People with acute or chronic infectious mononucleosis, as well as healthy virus carriers, act as the infection's source. Transmission occurs more frequently from asymptomatic infected individuals than from those exhibiting overt symptoms of mononucleosis. Many healthy individuals can spread the virus throughout their lives. An infected person can start spreading the virus shortly after contracting it. The primary mode of EBV transmission is through saliva, often via actions such as speaking, coughing, sneezing, kissing, or sharing utensils, and occasionally through a blood transfusion. This disease, sometimes dubbed the "kissing disease," leads to the lifelong presence of antibodies once contracted. The virus incubates for about six weeks, primarily replicating in the throat. Virus presence in the blood becomes detectable two weeks before the disease manifests.

Infants under one year of age receive antibodies through breast milk, which makes this infection rare in this age group. Children under five years typically contract the infection, presenting only mild upper respiratory symptoms, which complicates the suspicion and diagnosis of EBV in them. In adolescents and adults who contract the virus, 35-50% develop infectious mononucleosis. Over the past decade, from 2006 to 2016, the occurrence of infectious mononucleosis in Lithuania has gradually decreased but remains 2-3 times higher than the average in the European Union. According to ULAC data from January 2019, Lithuania reported 24 cases of infectious mononucleosis across various age groups.

Accompanying Symptoms

EBV-induced infections present symptoms such as a sore throat, swollen lymph nodes primarily in the neck and armpits, and less frequently in the groin, coupled with general weakness, headaches, and fever. Most patients report general malaise and loss of appetite in the prodromal period, followed by a fever that, in rare cases, may reach 40°C and last up to three weeks. The throat and tonsils generally appear red, and about a third of the patients may see grayish or greenish deposits on their tonsils. Around 80% of patients develop pharyngitis, 8% show splenomegaly, and 7% show hepatomegaly. Approximately 25% develop petechiae on the palate. Patients may experience both anterior and posterior cervical lymphadenopathy, unlike bacterial tonsillitis, which involves only anterior lymphadenopathy. Along with enlarged spleen, liver enlargement, and elevated liver enzyme concentrations occur in 80-90% of cases; these typically normalize after about 20 days. If treated with ampicillin or amoxicillin, a rash, which is not an allergic reaction to these antibiotics, may develop more commonly. Without medication, a rash appears in 4.2-13% of cases in acute infectious mononucleosis. However, when antibiotics are involved, the incidence of rash may surge to between 27.8-69%, and some studies on ampicillin even report 90%. Occasionally, patients might also experience periorbital edema. Jaundice, central nervous system complications, and myocarditis represent rare complications. As the fever subsides, symptoms of angina lessen, but lymphadenopathy may persist for 3-6 months. If symptoms extend beyond six months, the EBV infection becomes classified as chronic.

Continuation in the Internist Magazine No. 3