Cytomegalovirus
Cytomegalovirus (CMV) is a common
virus that infects people of all ages. It is a genus of Herpes
viruses which is known as Human herpesvirus 5 (HHV-5) in humans.
Cytomegalovirus is a member of
Betaherpesvirinae in the subfamily Herpesviridae along with
herpes simplex virus
types 1 and 2, varicella-zoster virus (which causes chickenpox and
shingles), and Epstein-Barr virus (which, together with CMV, are the
main causes for infectious mononucleosis). These viruses share a
characteristic ability to remain latent within the body over a long
period.
“Cytomegalovirus” means “very big cell virus”.
CMV can be spread by person to
person contact (kissing, sexual contact, and getting saliva or urine
on your, hands and then touching your eyes, or the inside of your
nose or mouth), through the breast milk of an infected woman who is
breast feeding, blood transfusions and solid organ transplantations,
and also from am infected mother to her unborn child.
CMV attacks the salivary glands,
and can be fatal to fetuses. For persons with HIV or who have had an
organ transplanted, CMV can be life threatening.
CMV
infection is thought to be specific to humans. The age at
presentation, clinical manifestations, and route of infection may
vary from person to person, but very few people escape infection
during their lifetime. Serologic surveys conducted worldwide
demonstrate CMV to be a ubiquitous infection of humans. Depending on
the population surveyed, CMV may be found in 40-100% of people,
depending on socioeconomic conditions. Infection earlier in life is
typical in developing countries, whereas up to 50% of young adults
are seronegative in many developed nations. CMV prevalence increases
with age. Age has also been found to be a risk factor for CMV
disease in certain transplant populations.
SIGNS AND SYMPTOMS
This virus usually produces few,
if any, symptoms and it periodically reactivates without symptoms.
Nevertheless, persons who have been infected with CMV develop
antibodies to the virus, which persist in the blood of the
individual for all his life.
A person may be infected with CMV if
he/she has symptoms of infectious mononucleosis (fever,
fatigue, sore throat and swollen LYMPH NODES)
but has negative test results for mononucleosis and Epstein Barr
virus, or, shows signs of hepatitis, but has negative test results
for hepatitis A, B, and C.
Symptoms are present 9-60 days after primary
infection.
There are several types of CMV
diseases:
Congenital CMV
Disease is one of the TORCH infections (toxoplasmosis,
other infections including syphilis, rubella, CMV, and herpes
simplex virus) which may affect the development of newborns.
Approximately 10% of congenitally infected infants have clinical
evidence of disease at birth. The most severe form of congenital CMV
infection is referred to as cytomegalic inclusion disease (CID). It
almost always occurs in women who have primary CMV infection during
pregnancy.
The syndrome
of congenital cytomegalic inclusion disease includes jaundice (yellowing
of the skin and eyes), splenomegaly (enlarged
spleen), thrombocytopenia (a low
platelet count), intrauterine growth retardation,
microcephaly (a condition, present at
birth, in which the head is much smaller than normal for an infant
of that age and gender), and retinitis (inflammation
of the retina, the light-sensitive tissue at the back of the
eyeball, that may lead to the loss of vision). Congenital CMV
may also be asymptomatic. This happens when the mother has a
preexisting immunity to CMV. These children appear normal at birth
but they can have subtle growth retardation compared to uninfected
children. The major consequence of asymptomatic CMV infection is the
loss of hearing.
Acquired CMV infection
occurs postnatally. Primary infection is usually asymptomatic
although CMV disease may occur in the following situations:
Perinatal Infection. This type of CMV infection
usually occurs secondary to exposure to infected secretions in the
birth canal or via breastfeeding. It can be symptomatic (lymphadenopathy(disease
or swelling of the lymph nodes), hepatitis, and pneumonitis(inflammation
of the lungs), which may be severe on occasion) or
asymptomatic.
CMV Mononucleosis. This is a
disease of young adults which is acquired by person-to-person
contact, by blood transfusions or solid organ transplantation. The
symptoms include fever and severe malaise, the presence of an
atypical lymphocytosis (increased numbers
of circulating lymphocytes) and mild elevation of liver
enzymes.
Transfusion-acquired CMV
infection. Posttransfusion CMV infection has a presentation similar
to that of CMV mononucleosis. Incubation periods range from 20-60
days.
CMV infections
in immunocompromised patients. Cytomegalovirus causes a variety of
symptoms in immunocompromised patients. Disease manifestations vary
in severity depending on the degree of host immunosuppression. Viral
dissemination leads to multiple organ system involvement, with the
most important clinical manifestations consisting of pneumonitis,
gastrointestinal disease, and retinitis.
There are several tests which help
detect the presence of these antibodies and they
are widely available from commercial
laboratories.
TREATMENT
No treatment is generally necessary
for CMV infection in the healthy individual since the majority of
infections resolve on their own. For immunocompromised persons the
treatment consists of antiviral agents:
Ganciclovir (Cytovene), Cidofovir
(Vistide), Foscarnet (Foscavir); immunoglobulins: Immune globulin
intravenous (Gamimune, Gammagard, Sandoglobulin, Gammar-P), CMV-Ig (CytoGam),
also a good nutrition. Vaccines are still in the research and
development stage.
PREVENTION
Prevention is very important for
pregnant or of childbearing age women. If you regularly come in
contact with a large number of children, particularly
in day care centre environments, you
should avoid behaviours known to be associated with transmission of
infection, particularly kissing and sharing eating utensils and
carefully wash your hands after diaper changes.
|
