Mononucleosis is primarily caused by which virus?

Mononucleosis is primarily associated with the Epstein-Barr virus (EBV), which is a member of the herpesvirus family. This virus is known for causing infectious mononucleosis, often referred to simply as "mono." The disease is characterized by symptoms such as fever, sore throat, swollen lymph nodes, and fatigue.

EBV infects B lymphocytes, a type of white blood cell, leading to an increase in atypical lymphocytes in the blood, which is a hallmark of the illness. While other viruses like cytomegalovirus (CMV) can also cause similar symptoms, EBV is the most common and classic cause of mononucleosis.

This association is well-documented in medical literature, making EBV the correct choice when identifying the primary cause of mononucleosis. In contrast, HIV is linked to a different set of symptoms and complications, while the influenza virus leads to respiratory illness rather than the distinct clinical picture of mononucleosis.