Infectious mononucleosis is a highly contagious viral disease caused by the Epstein-Barr Virus (EBV). EBV is in the herpes virus family, and is also known as human herpes virus type 4. EBV is found worldwide and infects about 90% of people by adulthood, although most people never show symptoms (Centers for Disease Control and Prevention [CDC], 2014). Occasionally, symptoms can recur later in life (CDC, 2014). Symptoms of infectious mononucleosis include fatigue, fever, nausea, sore throat, cough, body aches, rash, photophobia, swollen lymph nodes in neck and armpits, and rarely, splenomegaly (enlarged spleen) and hepatomegaly (enlarged liver). Most people are initially exposed to EBV during childhood and the symptoms are not distinguishable from any other mild childhood illness (CDC, 2014). EBV infection in adulthood may result in more severe and long-lasting symptoms, especially fatigue which can last up to several months (CDC, 2014).
EBV is transmitted via body secretions, including saliva, blood and semen (CDC, 2014). The virus is transmitted by children 10-14 days or by adults 30-50 days after infection (Chamberlain, 2010). The virus first replicates within the epithelial cells of the nasopharynx and then invades B lymphocytes via their CD21 receptors (Chamberlain, 2010). The infected B lymphocytes circulate all through the body spreading the infection throughout the reticular endothelial system (i.e., lymph system, spleen, liver) (Burke, 2014; Chamberlain, 2010). EBV-infected B lymphocytes trigger cellular-mediated and antibody-mediated immune system responses. The cellular-mediated T lymphocyte response results in the destruction of EBV-infected B lymphocytes by natural killer cells and CD8+ cytotoxic T lymphocytes (Burke, 2014; Chamberlain, 2010). The faster the T lymphocyte response, the milder the symptoms and the better the prognosis (Burke, 2014). Ineffective T lymphocyte response can result in the development of B cell lymphoma.
Fever is caused by cytokine release by the host immune system, subsequent to EBV infection of the B lymphocytes (Burke, 2014). Lymphocytosis (high lymphocyte count) is caused by an increased number of circulating activated B and T lymphocytes, also known as Downey cells (Chamberlain, 2010). Pharyngitis is called by EBV-infected B lymphocyte proliferation within the lymphatic tissue of the oropharynx (Burke, 2014). EBV infection is lifelong.
Symptoms of Infectious Mononucleosis
(Stöppler, & Shiel, 2013)
Characteristic rash of Infectious mononucleosis:
(Wolff, Goldsmith, Katz, Gilchrest, Paller, & Leffell; 2007)