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CMV is a virus within the herpes group of viruses, all of which tend to remain dormant in the body after an initial infection. There are two types of CMV infection: primary and recurrent. A primary infection is an individual’s first infection. A recurrent infection is either a reactivation of a prior infection or a reinfection with a new strain. An estimated 40% to 90% of adults have experienced infection and test positive for CMV antibodies.
The majority of people infected with CMV experience no symptoms and are therefore not even aware that they’ve been infected. In adults, infection may manifest in flu-like symptoms, such as fever, swollen glands, and sore throat. However, infection of a fetus or newborn can lead to brain damage or even death. Currently there is no effective treatment or vaccine.
How is CMV Transmitted?
CMV can be transmitted through urine, saliva, mucus, cervical secretions, semen, blood, or breast milk. However it is most common in settings such as day care centers, where children can transmit the virus through contact with each other’s bodily fluids (infected children carry the virus in their respiratory and urinary tracts for long periods of time). Adults can also be infected through unprotected sexual contact. An infected mother can transmit CMV to her fetus either through the placenta or through exposure to her infected cervical secretions during birth. CMV is transmitted when some one with an active infection comes into contact with some one who has never been exposed to it before.
Is There a Way to Screen for CMV?
A blood test can detect the presence of antibodies to CMV, which would indicate whether an individual had ever been infected with the virus. The presence of IgM (immunoglobulin M) antibodies indicates that the individual is experiencing either a primary or a current infection. The presence of IgG (immunoglobulin G) antibodies (reactive) indicates that an infection occurred at some point in the past. Therefore, a reactive (positive) IgG and non-reactive (negative) IgM result would indicate that an individual had experienced a past infection is not necessarily currently infectious.
How Are TSBC Donors Screened?
Prior to June 2010 all Donors were screened using the CMV Total Antibody blood test and CMV Urine Culture. If a donor's blood was CMV reactive the secondary screening was a CMV Urine Culture. The Donor's urine culture would have to be non-reactive in order for the donor to be included on the TSBC Catalog.
Currently, we screen all donors for the presence of CMV antibodies using two blood tests. If as a result of the CMV Total Antibody blood test the donor's blood is reactive for CMV Total antibodies, instead of using a Urine Culture we do a CMV IgG/IgM blood antibody test. This is a more sensitive screening test.
If the CMV IgM titer of the secondary CMV IgG/IgM blood antibody test is negative, the donor is presumed to be non-infectious (CMV IgM negative-CMV IgG positive shows historic CMV infection not current infection).
If CMV IgM titer of the CMV IgG/IgM blood antibody test is positive, the donor is presumed infectious, is put on hold for three months and his quarantined semen samples are destroyed. (CMV IgM positive-CMV IgG positive shows historic CMV exposure and current infection).
The donor’s blood is then periodically retested as part of our ongoing donor screening. If CMV IgM becomes positive from the last blood testing cycle, the donor’s quarantined semen samples are destroyed, he is put on hold for three months and then tested again.
While some of TSBC’s donors have antibody results consistent with previous infection (CMV Reactive or IgG Positive), no donors on the TSBC catalog has antibody results consistent with current or recent infection (CMV Reactive and IgM Positive).
Information on a donor’s CMV antibody status is included on his short profile.
• CMV IgG – negative: Donor has never been exposed to CMV
• CMV IgG – positive: Donor has historically been exposed to the CMV virus
• CMV IgM- negative: Donor is presumed non-infectious and is ok to release
• CMV IgM – positive: Donor is presumed currently infections and all vials from that testing period are destroyed and the donor is put on hold for a 3 month period. He will be tested again before any more vials will be released.
Should a Recipient Be Screened for CMV?
We recommend that you check with your own medical practitioner to decide whether you should be screened for CMV antibodies. Many doctors feel that one-time antibody screening is of limited value because antibody levels may fluctuate in the blood. If you do test positive for IgM antibodies, it would be advisable to confirm this result, much like we do with all of our donors. If the follow-up screen for CMV finds you negative for IgG there should be no concerns. If follow-up screen finds you positive for IgG, postpone insemination attempts until you are no longer infectious.
Is It Safe to Use a Donor Who Is Positive for CMV?
Yes, it is. Our screening process aims to identify donors who are positive for a past history of CMV infection, but do not have an active infection (see How Are TSBC Donors Screened below). Furthermore, our six-month quarantine policy ensures that should a donor test positive for a current or recent infection, his potentially infectious samples are destroyed before they are available for release to recipients.
You may wish to consult with your own medical practitioner as to whether he or she feels it is acceptable to use a donor who is positive for CMV IgG antibodies. Given our screening process, we presume that our donors who are positive for CMV IgG antibodies are non-infectious for CMV. Furthermore, our six-month quarantine policy ensures that should a donor test positive for a current or recent infection, we would destroy all his potentially infectious samples before they were ever released to recipients.