Chapter 184: Epstein Barr Virus Infections (Infectious Mononucleosis)

Patient Story

A 16-year-old boy comes to see his pediatrician because of a 7-day history of intense sore throat, fever, malaise, and abdominal pain. He also complains of bilateral neck swelling and tenderness. On examination, he has markedly enlarged tonsils with bilateral whitish exudates, and very large lymph nodes palpable in the posterior neck bilaterally (Figure 184-1). In addition, his spleen is palpable at 1 cm below the left costal margin. A heterophile antibody test (monospot) is positive and he is offered symptomatic treatment. His symptoms persist for about 10 days, after which he recovers completely.

Introduction

Epstein Barr virus (EBV) is a DNA virus that belongs to the Herpes virus family. It is the most common etiological agent of infectious mononucleosis, a clinical syndrome characterized by fever, pharyngitis and cervical lymphadenopathy. Rarely, encephalitis, myocarditis, and hemolytic anemia can develop as a consequence of EBV infections.¹ In the immunocompromised host, this virus can cause life-threatening infections.²

Synonyms

EBV infection is synonymous with infectious mononucleosis although infectious mononucleosis can be caused by other viruses such as cytomegalovirus (CMV). Other terms associated with EBV are glandular syndrome and human herpes virus 4. It is referred to as “the kissing disease” in the popular vernacular.

Epidemiology

• Ubiquitous in the environment.

• In developed countries, EBV infections are not common in infants and young children. In contrast, in developing nations, 90 percent of children less than 6 years of age have been exposed to the virus.^1,3,4

• The majority of primary infections occur in adolescents and young adults.

• By adulthood, greater than 90 percent have serological evidence of previous EBV exposure.

• The virus has no defined seasonal variations and occurs year round with slightly higher incidence during summer months.^5–7

• Oral secretions are the main source of transmission; that is, deep kissing, toddlers sharing toys.⁸

• In childhood, EBV infections may be asymptomatic.

• EBV infection results in infectious mononucleosis in 30 to 40 percent of adolescents.

• Incubation 30 to 50 days.

Etiology and Pathophysiology

• The virus infects epithelial cells in the tonsillar crypts and B lymphocytes.²

• The virus is disseminated throughout the reticuloendothelial system (tonsils, spleen, and lymph nodes) by the infected B cells.

• CD4 and CD8 T cell responses are activated.

• The virus establishes permanent latent infections in the host.

• Disease severity may be related to high numbers of NK and CD8⁺ T cells and elevated blood viral loads.⁸

Risk Factors

• In developed countries, teenagers and college students are the ...