Biology and epidemiology of the virus
Cytomegalovirus (the name derives from the Greek cytos — cell and megas — large) belongs to the family Herpesviridae, genus Cytomegalovirus. The pathogen was first isolated by researcher H. Rowe (K. Smith independently around the same time) in 1956. Among all herpesviruses, it possesses the largest DNA genome. In laboratory conditions, the virus replicates exclusively in human cells (fibroblasts, epithelial cells, macrophages), although its pathogenicity in monkeys has also been proven.
When cultured on fibroblasts, the virus exerts a pronounced cytopathic effect, causing the formation of specific intranuclear inclusions and giant cytomegalic cells. In the external environment, the pathogen is extremely unstable: it is thermolabile (destroyed by heat) and highly sensitive to standard disinfectants and fat solvents.
Sources and routes of transmission The infection is widespread. The only source of infection is humans — patients with a manifest form or asymptomatic carriers. The virus is actively shed in urine, saliva, semen, breast milk, and circulates in the blood.
The entry portals include mucous membranes, skin, respiratory tract, and placenta. The main transmission mechanisms include:
- Contact and respiratory (household and airborne).
- Fecal-oral.
- Sexual.
- Parenteral (via blood transfusion, organ transplantation).
- Transplacental (leading to congenital infection).
Pathogenesis and clinical presentation
In most cases, primary infection results in a latent form that persists for life. The virus exhibits a pronounced tropism for the epithelial cells of the salivary glands and renal tubules, where its replication takes place. The main reservoirs of latency are mononuclear lymphocytes and bone marrow stromal cells. The exact incubation period has not been established due to the frequent subclinical course.
Acute manifest forms or virus reactivation occur against the background of immunosuppression. The groups at highest risk are immunocompromised individuals, organ transplant recipients, and pregnant women. In 95% of AIDS patients, cytomegalovirus acts as a severe opportunistic infection.
Spectrum of clinical manifestations:
- Acquired infection: can lead to central nervous system damage with cognitive impairment, vision and hearing loss, as well as severe visceral pathologies such as pneumonia. One of the formidable complications is the triggering of Guillain–Barré syndrome — a demyelinating disorder of nerve roots accompanied by paresis and paralysis. The virus is also suspected to have oncogenic potential (e.g., a link to prostate adenocarcinoma development).
- Congenital infection: poses the greatest danger and is diagnosed in approximately 1% of newborns as a result of transplacental transmission. The clinical picture includes severe jaundice, hepatosplenomegaly, eye damage, cachexia, and multiple malformations (including microcephaly). The prognosis is often unfavorable and may lead to death.
Diagnostics, treatment, and prevention
In response to viral invasion, the body develops both humoral and cellular immunity. However, the production of specific virus-neutralizing antibodies does not prevent the persistence of the pathogen within cells.
Microbiological diagnostics Samples used for testing include blood, urine, saliva, breast milk, cerebrospinal fluid, and cervical secretions.
- Cytological method: aimed at detecting giant cells measuring 25–40 µm. When stained with hematoxylin and eosin, intranuclear inclusions are clearly visualized — forming the classic «owl-eye» appearance.
- Virological method: isolation of the pathogen in cell culture.
- Identification and serology: PCR, DFA, and ELISA with monoclonal antibodies are used to confirm the diagnosis. Serological diagnostics include the determination of specific IgM and IgG antibodies (using ELISA, complement fixation test, and neutralization test).
Principles of treatment and prevention Etiotropic therapy is based on nucleoside analogues (acyclovir, ganciclovir, foscarnet). Immunotherapy utilizes interferon inducers (poludan), interferons themselves, immunomodulators (levamisole), and normal human immunoglobulin.
There are no specific vaccines against cytomegalovirus. Non-specific prevention consists of strictly isolating risk groups from potential sources. It is important to note that children with congenital cytomegaly actively shed the virus into the environment up to 5 years of age. When planning a family, if a child with congenital CMV infection has already been born, it is strongly recommended to postpone the next pregnancy for at least 2 years to account for the duration of viral persistence in the mother.
Briefly: answers to topical questions
Which organs are affected in congenital cytomegalovirus infection?
In congenital cytomegalovirus infection, the central nervous system, sensory organs, liver, spleen, and lungs are primarily affected.
- Central nervous system — microcephaly, intellectual disability, speech disorders, and other severe neurological impairments develop.
- Sensory organs — deafness (sensorineural hearing loss) and eye damage, including chorioretinitis with subsequent optic nerve atrophy, are characteristic.
- Liver and spleen — hepatosplenomegaly and jaundice occur.
- Lungs — development of hematogenous interstitial pneumonia is observed.
The infection may also lead to cachexia and the formation of other developmental malformations.
What nervous system complications does cytomegalovirus infection cause?
Cytomegalovirus infection causes a number of severe complications affecting the central and peripheral nervous systems.
- Peripheral nervous system — the infection can trigger Guillain–Barré syndrome (a demyelinating disorder of nerve roots accompanied by paresis and paralysis).
- Central nervous system — microcephaly, intellectual disability, speech disorders, and other serious neurological impairments occur (especially in the congenital form).
- Sensory organs — sensorineural hearing loss (deafness) is characteristic, as well as ocular damage in the form of chorioretinitis with subsequent optic nerve atrophy.
It is easy to remember the main cytological marker: imagine a huge owl (cytomegaly = large cell) nesting in the salivary glands and kidneys. Its intranuclear inclusions under a microscope look exactly like an «owl's eye».
Class and exam questions
Why does the presence of CMV antibodies not guarantee protection against infection?
The formation of virus-neutralizing antibodies does not eliminate the pathogen. The virus persists intracellularly in mononuclear lymphocytes and stromal cells, reactivating whenever immunity is weakened.
Through which biological fluids can CMV be transmitted?
The virus is shed in virtually all secretions: it is present in saliva, urine, semen, breast milk, cervical secretions, and also circulates in blood and cerebrospinal fluid.
When is it safe to plan the next pregnancy after giving birth to a child with congenital CMV?
The medical recommendation is to postpone the next pregnancy for at least 2 years. This is due to the prolonged persistence of the virus in the mother's body.
What else to study on this topic
- Mechanisms of giant cell formation and in vitro cytopathic effect
- Pathogenesis of demyelinating lesions in Guillain–Barré syndrome
- Features of immune status in HIV infection and CMV reactivation
- Regimens of nucleoside analogues in cytomegalovirus pneumonia
- Oncogenic potential of herpesviruses using prostate adenocarcinoma as an example
Study the full topic in the «Microbiology» course
This is a summary. The course covers everything tested in classes and exams.
- Full study guide on «Cytomegalovirus» and 4,383 other subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 141 video lectures on the subject
Other topics in the section "DNA viruses (parvoviruses, papillomaviruses, adenoviruses, hepatitis B, herpes viruses, poxviruses, anelloviruses)"
Free video lessons: microbiologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.