The Epstein-Barr virus (EBV) is a member of the herpes virus family, and is responsible for many disorders including infectious mononucleosis, and other lymphoproliferative disorders. Herpes viruses are leading causes of viral infections worldwide, second only to the influenza and cold viruses. These viruses are important because they establish latency in B lymphocytes (a type of white blood cell or WBC), meaning they are never truly eliminated from the body and can pose a risk of reactivation under certain conditions. Reactivation of latent viruses is especially important in patients that have compromised or suppressed immune systems, such as immunodeficient patients (e.g., chemotherapy, HIV, organ transplant patients etc). In addition, two types of human cancers, Burkitt’s lymphoma and nasopharyngeal carcinoma, have been associated with EBV infection. There is no cure available for latent infections.
EBV infection is via exposure to oral secretions, usually by kissing, sharing food or utensils, or coughing. It can also be spread through blood transfusions and organ transplants. It does not survive outside the host and has not been recovered from any environmental sources. In the very young, EBV infections are generally asymptomatic. In adolescents the primary initial infection may be asymptomatic; however, the most common manifestation in this age group is infectious mononucleosis. In immunocompromised/ immunosuppressed patients, especially solid-organ transplant patients, there is a risk of developing a potentially fatal disorder called post-transplant lymphoproliferative disorder (PTLD). Although less common than in solid-organ recipients, EBV associated PTLD is also seen in bone marrow and blood stem cell transplant patients. In these populations, active EBV infection can result in high morbidity and mortality if left untreated.
Patients presenting with primary infection are generally diagnosed using serology testing. In normal, healthy individuals, once EBV has been identified as the causative agent, no further testing is required. Immunocompromised individuals, however, may not produce an appropriate serological response, and require testing using other methods. It is this population where EBV testing by molecular methods is beneficial. Also, once EBV has been identified in this population, either through primary infection or reactivation, it is important to know the amount of virus circulating in the patient in order to monitor disease progression and treatment outcome. Determining the amount of circulating virus is known as the “viral load.”
This assay detects the number of circulating EBV viral particles using polymerase chain reaction (PCR). This assay is not intended for diagnostic purposes in healthy individuals. Specimen types include serum, plasma, whole blood, and cerebral spinal fluid (CSF).