Epstein-Barr Virus (EBV)

• Epstein-Barr Virus (EBV) is also known as kissing disease or infectious mononucleosis (mono).
• EBV is a double-stranded and linear DNA virus belonging to the Herpesviridae family.
• It is an enveloped virus.
• Transmission occurs through saliva, such as kissing or sharing toothbrushes and cups; blood transmission is rare.
• Over 90% of adults in the U.S. have antibodies against EBV, indicating widespread infection.
• EBV infection is often asymptomatic in the first few years of life.

Immune Response to EBV

• An overactive immune response to EBV can cause infectious mononucleosis (mono).
• Mono is characterized by fever, pharyngitis, and swollen lymph nodes.
• Symptoms result from immune cells attacking infected cells.
• Ineffective immune control of EBV can lead to lymphoproliferative diseases.
• Lymphoproliferative diseases involve abnormal growth of lymphocytes, such as Burkitt lymphoma and Hodgkin's lymphoma.
• Both EBV-specific and non-specific (heterophile) antibodies are produced during infection.

Diagnosis

• Diagnosis is based on symptoms, lymphocytosis (increased lymphocytes), and atypical lymphocytes.
• Atypical lymphocytes make up 30% of the white blood cell count, with mononuclear cells comprising 60-70%.
• The heterophile antibody test (Monospot test) is commonly used for early diagnosis.

Treatment and Prevention

• There is no specific antiviral therapy needed for uncomplicated infectious mononucleosis.
• High doses of acyclovir may be used in life-threatening cases.
• There is currently no vaccine for EBV.
• Penicillin should be avoided during EBV infection due to the risk of a maculopapular rash.

Pathogenesis and Associated Conditions

• EBV infects B cells, which can lead to abnormal growth due to the inability of cytotoxic T lymphocytes (CTLs) to kill infected cells.
• This can result in B cell cancers, including Burkitt’s lymphoma, Hodgkin's lymphoma, non-Hodgkin's lymphoma, and primary CNS lymphomas.
• Infection of the nasopharynx can cause abnormal proliferation, leading to nasopharyngeal carcinoma.
• EBV can cause hairy leukoplakia, characterized by white plaques on the tongue.

Classic Triad and Additional Symptoms

• The classic triad of symptoms includes pharyngitis, lymphadenopathy, and fever.
• Other common symptoms are splenomegaly, hepatomegaly, increased liver enzymes in the blood, headache, and malaise.
• Hepatitis is frequently seen, and encephalitis can occur in some patients.
• Splenic rupture is associated with contact sports.
• Palatal petechiae (small, red or purple spots) may appear on the soft palate.

Epidemiology

• EBV infection is more common in adolescents and young adults (15-24 years).

Additional Key Points

• Double-stranded DNA viruses are divided into Herpesviridae and Poxviridae families.
• These viruses depend less on the host for replication.
• Virus-encoded proteins play a significant role in replication, facilitating the development of antiviral drugs.
• EBV remains latent within B lymphocytes.
• Activated T cells appear as atypical lymphocytes, also known as Downey cells.
• The typical infectious mononucleosis syndrome appears after an incubation period of 4-7 weeks; complete recovery may take much longer.
• EBV was the first human cancer virus to be discovered.
• HIV-infected individuals exposed to EBV may develop oral hairy leukoplakia.