Commonly Asked Questions
- What is CMV?
CMV is the abbreviation for cytomegalovirus. Exposure to this virus is quite common; about 50 to 85 % of people test positive for CMV in the US. An initial infection manifests as a mild cold, and symptoms related to this infection resolve quickly. Many people who acquire CMV were never symptomatic and most people do not know whether they have ever been infected.
- How do people contract CMV?
CMV is passed from infected people to others through body fluids. It can also be transmitted through transplanted organs, blood transfusions, and through sexual contact. Most people are most likely to be exposed to the virus through contact with a person (often young children) who has an active (recent) CMV infection. The actively infected person is highly contagious because at that moment there is a lot of virus in the system and virus is actively shedding in body fluids. Eventually, one’s immune system controls the infection and viral levels go down dramatically. This person is now said to have a “remote” infection and is considered completely recovered. A person with a normal immune system* is unlikely to get CMV from a recovered previously infected individual.
* Examples of abnormal immune system = people undergoing chemotherapy, stem cell transplant, organ transplant, AIDS
- What is the significance of CMV and pregnancy?
CMV does not usually cause problems in healthy people, but it can be dangerous to a developing fetus if a previously unexposed (CMV negative) mother becomes infected with the virus while pregnant. The virus will not harm most babies in this circumstance, but a small number suffer developmental abnormalities such as hearing loss and mental retardation.
- How does a sperm bank test sperm donors/sperm client depositors for CMV?
Typically, CMV is contracted from people in the environment who are acutely ill with CMV and actively shedding virus. Because CMV may be transmitted in fluids like semen, there is also a theoretical risk that one could transmit this virus to a CMV negative woman through a procedure like an intrauterine insemination, though empirically, this risk only occurs if the semen donor was acutely ill with CMV at the time of sperm donation. For this reason, the FDA mandates the screening of anonymous and directed semen donors for CMV status. A man who is currently actively infected with CMV will not be a suitable semen donor.
- How do you interpret CMV status test results?
CMV status is determined based on a serologic study (a test that looks for the presence of antibodies in the blood). The initial screening test is a "total antibody test". Anybody who has ever been infected with CMV will have a positive total antibody test. If positive, we test further to detect which specific antibodies are elevated. If the infection is recent / active, the IgM antibody level will be elevated. If the infection is remote and the person has fully recovered, typically only the IgG antibody will be detected.
People who are CMV IgG positive, IgM negative are considered immunized, and not actively infectious. The FDA allows people with such profiles to donate semen for procreative use either as anonymous or directed donors. Procreation through use of a surrogate is considered a direct donation.
On occasion, we augment the antibody test by screening the urine for shedding of CMV nucleic acid with a PCR test. This test may be useful to differentiate active infection from remote infection in the rare circumstance that IgM antibodies are detectable long after the acute phase.
- What is the significance of IgG versus IgM?
IgM antibodies are the first to respond to infections. When IgM is elevated, it’s typically an indication that the immune system is fighting a primary infection. The number of IgM antibodies decline as the immune system switches to making IgG antibodies. In most circumstances, these become the only antibodies detectable for a given virus. IgG antibodies will be present and detectable forever, indicating immunity to a given infection. A person who was once infected with CMV but has fully recovered from the acute infection will typically be IgM negative and IgG positive.
- Why are people totally antibody positive but negative for IgM and IgG?
The "total antibody test" is a screening test. By design, it detects all antibodies to CMV, including IgG and IgM. Screening antibody tests are known to occasionally detect antibodies that may be similar in structure to those directed at a certain virus, but are not clinically relevant or meaningful. These non-specific antibodies, sometimes called "cross-reacting antibodies" may cause the total antibody screening result to be back positive, however, the subsequent IgG and IgM specific test will be negative. It's the presence of specific IgG or IgM antibodies to CMV that tell us the CMV status of an individual: a current or recent infection, a remote infection, or no history of infection. California Cryobank provides you and your physician with results of the total antibody screening test and the specific tests for IgG and IgM so that you can discuss the findings with your doctor.
- Can a woman use a CMV positive sperm donor if she's CMV negative?
According to published literature, the risk of acquiring CMV from a healthy man with a history of a remote CMV infection is very low. The risk is further lowered if you use washed sperm (IUI vials). This is because the method used to prepare IUI vials significantly reduces the presence of white blood cells, the cells that are most likely to harbor the virus. Women who are undergoing IVF would empirically have an even lower risk of acquiring CMV. This is nevertheless a decision that you should make after speaking to your physician.