Abstract
Cytomegalovirus (CMV) is a double-stranded DNA virus and is a member of the Herpesviridae family.
For women of reproductive age, the greatest risk for exposure is through contact with the urine or saliva of young children.
Introduction
Cytomegalovirus (CMV) is a double-stranded DNA virus and is a member of the Herpesviridae family.1
For women of reproductive age, the greatest risk for exposure is through contact with the urine or saliva of young children.1
Routes of Transmission of Maternal Infection
CMV-infected individuals shed the virus in body fluids, such as urine, saliva, blood, tears, semen and breastmilk. CMV is spread from an infected person in the following ways:
1. From direct contact with urine or saliva, especially from babies and young children
2. Through sexual contact
3. From breastmilk
4. Through transplanted organs and blood transfusions1
Prevalence
A) In developed countries:
Up to 70 per cent of the population are infected.
In the United States, over 50 per cent of adults by age 40 have been infected with CMV.
The prevalence of congenital CMV infection has been reported to vary from approximately 0.2 per cent to 2 per cent.2
B) In developing countries:
Over 90 per cent of people are ultimately infected.
The congenital CMV birth rates ranged from 0.6 per cent to 6.1 per cent (systematic review of 11 population-based studies).3 [EL 1]
Signs and Symptoms of Maternal Cytomegalovirus
Most people are asymptomatic. But if symptoms occur:
1. Fever
2. Night sweats
3. Tiredness and uneasiness
4. Sore throat
5. Swollen glands
6. Joint and muscle pain
7. Low appetite and weight loss
Above symptoms will generally disappear after two weeks.
Types of Maternal Infection during Pregnancy
1. A new first-time infection during the pregnancy
2. A reinfection with a different CMV strain
3. A reactivation of a previous infection
Primary Maternal Infection
Primary maternal CMV infection during pregnancy usually occurs following contact with infected bodily fluids such as urine or saliva, especially from young children.2 Infection can be also acquired through sexual contact, transfusion of blood and blood products, whereas airborne infection is unlikely.
After a primary CMV infection, the virus remains dormant but reactivation and viral shedding is common. Reinfection with a different strain of the virus has also been reported.3
Primary maternal infection is responsible for 25 per cent of congenital CMV infections in the United States.2
Clinical Picture of Primary Maternal Infection
Ninety per cent of women with primary CMV infection are asymptomatic.
Symptomatic group may present with non-specific symptoms (fever, headache, pharyngitis, myalgia, arthralgia and fatigue).
Reactivation or reinfection with a different strain passes without clinical manifestations.
Diagnosis of Maternal Cytomegalovirus Infection
1 History
The majority of primary HCMV infections in immunocompetent individuals are clinically asymptomatic.
Fewer than 5 per cent of pregnant women with primary infection are reported to have symptoms.
However, careful clinical history may be extremely useful for detecting minor clinical symptoms and dating the onset of infection.
In a survey involving 244 pregnant women with primary HCMV infection, clinical symptoms were present in 166 (68.1%), with fever (60.2%), fatigue (48.8%) and headache (26.5%) being the most frequent symptoms.4 [EL 2]
2 Immune Responses
○ CMV-specific IgM antibodies are produced during the primary infection and persist for three or four months.
○ However, immunocompromised individuals may fail to produce IgM with primary infection. The presence of CMV IgM cannot be used by itself to time the infection or diagnose primary CMV infection because IgM can also be present during secondary CMV infection, which includes reinfection with a different strain or reactivation of latent CMV acquired in the past.
○ IgM-positive results in combination with low immunoglobin G (IgG) avidity results are considered reliable evidence for primary infection.
Immunoglobulin G (IgG)
○ Measurement of CMV IgG in paired samples taken one to three months apart can be used to diagnose primary infection.
○ Seroconversion (first sample IgG negative, second sample IgG positive) is clear evidence for recent primary infection.4
○ Specific IgG of low avidity is an excellent single serum indicating recent primary infection within the last three months.5
3 Viral Isolation, Detection of Virus and Viral Products in Maternal Blood
CMV can be recovered from multiple body fluids such as saliva, urine and vaginal secretions for a variable period.
The isolation of the virus from these sites confirms infection, but will not differentiate between a new primary or recurrent infection.
However, virus detection in blood has been reported to be diagnostic of primary CMV infection in immunocompetent individuals.
Diagnosis of Recurrent Maternal CMV Infection
Recurrent infection occurs when the initial CMV infection reactivates during pregnancy or due to a different CMV strain.4
IgG avidity describes the proportion of IgG bound to the antigen following treatment with denaturing agents.
A high IgG avidity index of 70 CMV at 6–18 weeks’ gestation can identify all women who would have an infected fetus/newborn (100 per cent sensitivity).5
Congenital CMV Infection
1. In about 30 per cent of cases, congenital infection passes from mother to baby when a previous latent CMV reactivates during pregnancy.
2. Only about 1–7 per cent of women are infected for the first time with CMV (primary CMV) during pregnancy; 30–40 per cent of those with primary infection will pass it on to the baby.6
3. About 10–15 per cent of babies with congenital infection will have symptoms at birth; up to 60 per cent of these will have serious complications later in life.
Fetal Implications of Congenital CMV
1. Miscarriage
2. Growth restriction
3. Intrauterine death
4. Microcephaly
5. Hepatosplenomegaly6
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