General Characteristics and Epidemiology
Basic features of CMV
- Also known as HHV-5
- Family: Herpesviridae
- Subfamily: Betaherpesvirinae
- Genus: Cytomegalovirus
- DNA virus:
- DNA core
- Icosahedral nucleocapsid
- Phospholipid envelope with glycoprotein spikes
- Approximately 60%–90% of adults have CMV antibodies (lifelong latent infection).
- Prevalence increases with age.
- Ethnicity: higher prevalence in non-Hispanic Black Americans and Mexican Americans
- Higher positivity rates also associated with:
- Female sex
- Birthplace outside the United States
- Low household income and education
- Household crowding
The CMV strain associated with human infection is found only in humans.
- Contact with infected bodily fluids
- Sexual contact
- Blood transfusion
- Organ transplantation
- In utero (during maternal viremia)
- During birth (from contact with vaginal secretions)
- Breast milk
- Occupational exposure
Host risk factors
Immunocompromised patients are at increased risk of morbidity and mortality from CMV.
- Transplant patients
Viral replication cycle
- Viral glycoproteins attach to host cell receptors → endocytosis or fusion with cell membrane (unclear)
- Capsid transported to the nuclear pore → DNA released into the nucleus
- Transcription and replication → viral assembly
- Budding through the nuclear membrane → assembly with tegument proteins
- Acquires envelope → released from cell
- Virus infects oral epithelial cells → viral replication → cytomegalic cells with owl’s eye nuclear inclusions
- Cell-mediated response ensues (most important for controlling CMV infection) → virus become latent in:
- Myeloid progenitor cells in the bone marrow
- Immunocompromised state → reactivation can occur → viremia → clinical manifestations
Cells infected with CMV will:
- Contain viral inclusion bodies (owl’s eye).
Diseases caused by CMV
The spectrum of clinical presentations with CMV is diverse and depends on the immune status of the host.
Most immunocompetent patients will be asymptomatic. In the minority who are symptomatic, the most common presentation is a syndrome similar to infectious mononucleosis (EBV).
- Clinical presentation:
- Myalgias and arthralgias
- Erythematous, maculopapular rash in patients exposed to beta-lactam antibiotics
- Less common:
- Lymphocytosis with atypical lymphocytes
- Negative heterophile (monospot test)
- Serology for CMV antibodies
- PCR for CMV DNA
- Management: Most cases are self-limited and do not require antiviral therapy.
Congenital CMV is one of the perinatal TORCH (toxoplasmosis, other agents, rubella, cytomegalovirus, and herpes simplex) infections.
- Most infants with congenital CMV infection are asymptomatic at birth.
- Symptomatic infants present with:
- Petechial rash
- Intrauterine growth restriction
- Sensorineural hearing loss
The following are rare in immunocompetent hosts and are often the result of reactivation of a latent infection. Note: Infections outside the lymph nodes, spleen, and liver are considered AIDS-defining conditions.
- GI manifestations:
- Neurologic manifestations:
- Guillain-Barré syndrome
- Ocular manifestations:
- Cardiopulmonary manifestations:
Comparison of Herpesviruses
The following table compares the 9 herpesviruses considered endemic in humans; there are 115 known species of herpesviruses, grouped into 3 families:
- Alpha (infect epithelial cells and produce latent infection in postmitotic neurons)
- Beta (infect and produce latent infection in a variety of cell types)
- Gamma (produce latent infection mainly in lymphoid cells)
|HHV||Common name||Primary target cells||Latency site||Clinical presentation*|
|HSV-1||Mucoepithelial cells||Dorsal root ganglia|
|EBV||Epithelial cells B cells||Memory B cells|
|CMV||Hematopoietic progenitor cells in bone marrow|
| 6A, 6B|
|Kaposi’s sarcoma–associated herpesvirus||B cells||Kaposi’s sarcoma|
VZV: varicella-zoster virus
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