Infectious Mononucleosis

Infectious mononucleosis is usually caused by primary infection with Epstein–Barr virus (EBV). The virus enters through the oropharynx, infects epithelial cells and B lymphocytes, and then establishes lifelong latency. The person’s immune response to infected B cells produces much of the illness: fever, pharyngitis, swollen lymph nodes, profound fatigue, and the atypical lymphocytes seen on the blood film. This mechanism explains why the illness can feel disproportionate to the throat findings. The immune response is widespread even though the initial portal of entry is the oropharynx. EBV also has an affinity for lymphoid tissue, so the spleen may enlarge as it participates in the immune response. An enlarged spleen is vulnerable to rupture, particularly with impact or strenuous exertion. EBV is transmitted mainly in saliva. A person may therefore spread the virus through kissing or sharing beverages, utensils, toothbrushes, or other items contaminated with saliva. Routine precautions are generally sufficient in care settings unless another infection-control indication exists.