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Epstein-Barr Virus (aka, HHV-4)

Epstein-Barr virus, aka, Human Herpesvirus 4
  • This virus has been characterized as a B-cell parasite because of its tropism for these immune cells.
  • Because it is transmitted in saliva, the virus is sometimes referred to as the "kissing disease."
– The virus can also be transmitted via saliva on shared cups or utensils.
  • The virus is very common: approximately 90% of adults have formed antibodies against the Epstein-Barr Virus (EBV).
  • Infection is usually mild or asymptomatic; we'll focus the rest of the tutorial on some important exceptions.
Infectious Mononucleosis
  • Most often develops in older children and adolescents.
  • Active infection of B cells leads to B-cell proliferation and T-cell activation.
  • Activated B cells produce heterophile antibodies
– Can be useful for diagnostic purposes.
  • Downey Cells: EBV-activated T-cells.
– In the histological image, we can see their irregular, almost fluttery appearance that some have compared to a ballerina's tutu.
  • Mononucleosis Symptoms
– Swollen lymph nodes, especially in the neck – Pharyngitis, due to the presence of infection in the tonsils – Splenomegaly, which, in rare cases, can lead to splenic rupture (this is why patients are advised to avoid contact sports or other activities that increase the risk of rupture). – Fatigue – Neurologic complications are possible: Meningoencephalitis and Gullain-Barr Syndrome.
  • Following primary infection, latent infection is established; reactivation of the virus promotes its shedding.
  • Lymphomas
  • EBV is associated with some lymphomas, including Burkitt lymphoma, African Burkitt lymphoma, and Hodgkin lymphomas
– Poor T-cell immunity
  • Post-transplant lymphoproliferative disorder
  • In transplant recipients, EBV is associated with post-transplant lymphoproliferative disorder.
  • Nasopharyngeal carcinoma
  • In some Asian populations, the virus is associated with nasopharyngeal carcinoma.
  • Hairy oral leukoplakia
  • In AIDS patients, the virus is associated with hairy oral leukoplakia, which is characterized by whitish plaques in the oral cavity.