Generality
Cytomegalovirus (abbreviated as CMV) is an ubiquitous (ie very common) virus, belonging to the herpes virus family.
To the family of herpes viruses belong other rather well-known pathogens, such as the varicella virus, the shingles virus, the cold sores virus and the mononucleosis virus (Epstein-Barr).
What is cytomegalovirus?
Cytomegalovirus is a fairly common viral genus, which belongs to the large family of herpes viruses, just like the more famous herpes simplex virus, varicella virus, shingles virus and Epstein-Barr virus ( mononucleosis ).
In healthy people, cytomegalovirus is responsible for asymptomatic or mildly symptomatic infections, spontaneous resolution and without long-term consequences. For these characteristics, the cytomegalovirus could be of little interest from the medical-clinical point of view, if it were not that it is capable of:
- "Hiding" in human bone marrow cells (example of viral latency ), only to be reactivated in the event of a generalized reduction of the immune system
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- Cause serious consequences, as soon as it is infected
- people with inefficient immune systems, such as AIDS patients or organ transplants,
- pregnant women (NB: if in the first case the serious consequences directly affect the infected person, in the second case they are at the expense of the future unborn child).
Epidemiology
Exposure to cytomegalovirus involves many people, all over the world. In this regard, epidemiological data are fairly clear and state that:
- In underdeveloped countries, cytomegalovirus has infected more than 90% of people at least once in their life;
- In the countries of the so-called Western world, 60-80% of adults have anti-cytomegalovirus antibodies in serum;
- Still in the countries of the so-called Western world, 40% of children have already acquired cytomegalovirus infection already at school age.
History
The discovery of the cytomegalovirus dates back to 1881 and the merit of this finding lies with a German pathologist named Hugo Ribbert .
Features
Cytomegalovirus is a double-stranded DNA virus; in other words, its genetic material consists of a DNA molecule, consisting of two chains (or filaments) of nucleotides, joined together and complementary to each other.
Cytomegalovirus is a virus with a pericapside (or envelope ), has a mostly spherical shape and measures about 150-200 nanometers in diameter; under the pericapside, it presents the classic viral capsid, whose symmetry is icosahedral.
During the phase of infection of a human being, the cytomegalovirus enters the cells of the infected subject through a mechanism of endocytosis and exploiting its characteristic glycoproteins; once inside the attacked cells, it goes to locate itself in the nucleus of the latter and, here, it begins to replicate itself, using the host's nuclear enzymes (NB: the viruses lack a complete self-replication apparatus, therefore they exploit that present in host cells, as if they were parasites).
Transmission
Transmission to a new cytomegalovirus host can take place in various ways:
- Through direct contact with oro-pharyngeal, vaginal or spermatic secretions, clearly belonging to an infected person;
- Through direct contact with tears, urine or feces of a person with the ongoing infection;
- Through breast milk, in a context of post-pregnancy breastfeeding (obviously this circumstance implies that the new host is the newborn and that the infecting subject is the mother);
- By transplacental route, in the context of a pregnancy (to find out more, see the dedicated sub-chapter);
- By transfusion of infected blood or blood products;
- Following a bone marrow or organ transplant (eg, kidney transplant).
Transmission of the cytomegalovirus infection from mother to fetus during pregnancy
The passage of the cytomegalovirus infection from the infected mother to the fetus, during a pregnancy, is an example of vertical transmission, by transplacental route, of an infectious disease.
Responsible for a condition known as congenital cytomegalovirus infection and having a frequency of 3 pregnancies every 10 at risk, the transplacental transmission of the cytomegalovirus is a very feared phenomenon and raises many concerns in the health sector, as it has serious consequences for the future unborn child.
Events similar to the vertical transmission of the cytomegalovirus from the mother to the fetus, but with less serious consequences, are the phenomena of passage of CMV infection from mother to child, during childbirth or the subsequent period of puerperium and breastfeeding.
In which periods of life is it easier to contract cytomegalovirus?
The periods of the life of a human being in which it is easier to contract cytomegalovirus infection are in particular two: childhood and the period between puberty and early adulthood, period, the latter in which the environmental promiscuity (kindergartens, schools, etc.) and sexual facilitates the direct transmission of the virus.
Symptoms and complications
To learn more: Symptoms Cytomegalovirus infection
As anticipated, in healthy people, the cytomegalovirus tends to cause a mild clinical, asymptomatic or slightly symptomatic infection (paucisintomatica); in those rare cases in which the cytomegalovirus is responsible for a substantial and evident symptomatology, the symptoms of the infection in progress are very reminiscent of those of a common influence; in fact, they generally consist of:
- Fever equal to or greater than 38 ° C;
- Chills;
- General malaise;
- Sore throat;
- Fatigue;
- Muscle pains;
- Enlarged lymph nodes;
- Articolar pains;
- Loss of appetite.
Curiosity
Sometimes the symptoms resulting from a cytomegalovirus infection are confused by the typical symptoms of mononucleosis.
Consequences of congenital cytomegalovirus infection
Congenital cytomegalovirus infection can have various consequences, including:
- Premature birth, with all the effects that this phenomenon entails;
- Low birth weight, with all the effects that this phenomenon entails;
- Jaundice;
- Presence of an enlarged and poorly functioning liver;
- Rash characterized by purple spots all over the body;
- Microcephaly (ie limited development of the skull, generally due to a limited development of the brain);
- Presence of an enlarged spleen;
- Presence of pneumonia;
- Presence of epilepsy.
Symptoms of cytomegalovirus infection in immunosuppressed individuals
In subjects with an inefficient immune system (eg, AIDS patients), cytomegalovirus infection can affect the functionality of various organs, including eyes, lungs, liver, esophagus, stomach, intestine and brain, and determine symptoms such as :
- Loss of vision, following retinal inflammation (retinitis);
- Digestive problems, due to inflammation of the intestine (colitis), stomach (gastritis), esophagus (esophagitis) and / or liver (hepatitis);
- Neurological problems, resulting from inflammation of the brain (encephalitis);
- Pneumonia.
Complications in healthy subjects
Rarely, in healthy subjects the infection with cytomegalovirus degenerates into complications; however, when it does, it causes a condition comparable to mononucleosis.
Complications of congenital cytomegalovirus infection
In addition to severe symptoms, congenital cytomegalovirus infection can give rise to several serious complications, including:
- Sensitive hearing loss;
- Intellectual deficits;
- Permanent visual deficits;
- Epilepsy;
- Loss of coordination skills;
- Muscle weakness.
Complications of cytomegalovirus infection in immunosuppressed
In immunosuppressed subjects, in addition to compromising the functioning of organs such as the lungs, liver, esophagus, intestine etc., cytomegalovirus infection can probably lead to death.
DANGER OF CITOMEGALOVIRUS LATENCE IN IMMUNODEPRESSI
Very skilled in containing the spread of cytomegalovirus infection, the immune system of a human being is often unable to eradicate the aforementioned virus permanently.
As stated, this incapacity implies that CMV goes to "hide" in the bone marrow cells of the infected subject, remaining so to speak clinically silent (or latent), until a temporary general weakening of the immune system does not capture the aforementioned subject (NB : this debilitation is often a consequence of a moment of stress); in such circumstances, in fact, the cytomegalovirus reactivates giving rise to a secondary infection .
In a healthy individual the phenomenon of cytomegalovirus reactivation does not cause any particular problems. On the contrary, in an immunodepressed individual (for example due to AIDS or immunosuppressive therapies resulting from an organ transplant) the reactivation of CMV has a high probability of causing the same serious consequences reported in the case of primary infections in immunosuppressed (ie, vision problems, digestive problems, neurological problems and even death).
In essence, therefore, while in healthy subjects the secondary infection with cytomegalovirus is clinically irrelevant, in subjects with an immunodepression it is a particularly feared and dangerous event.
When should I go to the doctor?
When affecting immunosuppressed individuals, pregnant or breastfeeding women and all infants born to infected women, cytomegalovirus infection is a clinical condition that deserves immediate medical attention.
In subjects in good health, CMV infection is not a particularly worrying phenomenon, except in those circumstances in which it determines a form of mononucleosis.
Diagnosis
The diagnosis of a cytomegalovirus infection in a healthy individual is not at all easy, as the aforementioned condition is, as stated several times, asymptomatic.
Interpretations of the antibody profile
To understand, from an examination of antibodies, when an individual has or has not been infected with cytomegalovirus, it is necessary to observe the immunoglobulins of type G (IgG) against CMV; indeed:
- If the IgG against CMV are absent, it means that the subject examined has never come into contact with the cytomegalovirus. In these situations, we speak of cytomegalovirus negative IgG ;
- If the IgG against CMV are present, it means that the subject examined has been exposed to cytomegalovirus in the past and has developed (towards the latter) an immunological memory. In such circumstances, doctors talk about positive cytomegalovirus IgG .
To this information, it is necessary to add those inherent to the antibody profile of a person with an existing cytomegalovirus infection. On such occasions, the immunoglobulins to be observed are IgM, which will be strongly present ( Cytomegalovirus IgM positive ), in those affected, while they will be absent ( Cytomegalovirus IgM negative ), in those who are not affected.
For the dangers that lie behind congenital cytomegalovirus infections, the evaluation of antibodies against CMV is a particularly important diagnostic investigation for women of childbearing age, who want to have a child.
Therapy
In light of what has been said so far, in the subject in good health, the infection with cytomegalovirus generally does not require any treatment .
On the other hand, the therapeutic argument relating to immunosuppressed patients (with primary or secondary infection) and newborn patients with the congenital form of CMV infection is totally different. In these circumstances, in fact, it is necessary to plan a specific therapy, based on the administration of antiviral or similar drugs, such as, for example:
- Ganciclovir ;
- Valganciclovir ;
- Foscarnet ;
- Cidofovir ;
- Anti-CMV immunoglobulins .
Curiosity: what happens in case of mononucleosis?
In general, for subjects in good health who develop mononucleosis due to cytomegalovirus, a brief hospitalization is expected, but without the administration of any antiviral drug.
Ganciclovir
Administered intravenously, Ganciclovir is the first antiviral drug historically approved for the treatment of cytomegalovirus infections and represents the preferred pharmaceutical preparation against the latter.
It may have several side effects, including: fever, rash, diarrhea, anemia, leukopenia and thrombocytopenia.
valganciclovir
Administered orally, Valganciclovir can be associated with the use of Ganciclovir or replace it during the treatment of milder cytomegalovirus infections.
Doctors could also use Valganciclovir for prophylactic purposes.
Foscarnet
Foscarnet acts with a mechanism different from Ganciclovir and, for this reason, it represents a drug that doctors prescribe when the infection with cytomegalovirus is resistant to treatment based on Ganciclovir.
Foscarnet is toxic to the kidneys and can cause episodes of convulsion.
Cidofovir
Cidofovir is an antiviral medicine prescribed in the presence of cytomegalovirus infections resistant to both Ganciclovir and Foscarnet.
Also toxic to the kidneys, Cidofovir is used mainly in AIDS patients.
Anti-CMV immunoglobulins
Anti-CMV immunoglobulins are often used in combination with Ganciclovir to treat cytomegalovirus infections that have caused episodes of pneumonia.
Prognosis
For healthy people, the prognosis of cytomegalovirus infections is generally positive.
As said on more than one occasion, instead, for immunocompromised subjects and for newborns suffering from a congenital infectious form, the prognosis can be ominous, since the cytomegalovirus can have permanent and sometimes deadly consequences.
According to some statistics, 80% of children with a congenital cytomegalovirus infection grow healthy and in good health.
