Final answer:
The primary agent of Infectious Mononucleosis is the Epstein-Barr virus (EBV), which is widespread and commonly causes symptoms like fatigue, fever, and sore throat. EBV can lay dormant but cause active infections such as mononucleosis and Burkitt lymphoma. Cytomegalovirus (CMV) can also cause a form of mononucleosis, especially in immunocompromised individuals.
Step-by-step explanation:
Infectious Mononucleosis Agent
The causative agent of Infectious Mononucleosis is often the Epstein-Barr virus (EBV), also known as Human herpesvirus 4 (HHV-4). Infectious Mononucleosis, sometimes referred to as 'mono' or 'the kissing disease', is commonly associated with symptoms such as fatigue, fever, sore throat, and enlarged lymph nodes. While EBV is the primary virus associated with mononucleosis, it can also be caused by other viruses, such as Cytomegalovirus (CMV), another member of the herpesvirus family, specifically Human herpesvirus 5 (HHV-5).
EBV resides within B lymphocytes and can remain latent for an extended period before emerging as active infections like mononucleosis or Burkitt lymphoma. Although most EBV infections are asymptomatic, when symptoms do present, they generally include the characteristic signs of mononucleosis noted above. CMV can also cause a mononucleosis-like syndrome, particularly in immunocompromised individuals, but tends to have milder signs when compared to EBV. CMV is also notable for serious congenital infections and diseases in immunocompromised adults.
To answer the student's question directly, Epstein-Barr virus (option a.) is the primary agent of Infectious Mononucleosis, although Cytomegalovirus (option b.) can also cause a mononucleosis-like illness.