Micrograph of CMV placentitis. Most infections with CMV go undiagnosed, as the virus usually produces few, if any, symptoms and tends to reactivate intermittently without symptoms. Persons who have been infected with CMV develop antibodies to the virus, which persist in the body for the lifetime of that individual. A number of laboratory tests that detect these antibodies to CMV have been developed to determine if infection has occurred and are widely available from commercial laboratories. In addition, the virus can be cultured from specimens obtained from urine, throat swabs, bronchial lavages and tissue samples to detect active infection. Both qualitative and quantitative polymerase chain reaction (PCR) testing for CMV are available as well, allowing physicians to monitor the viral load of people infected with CMV. The CMV pp65 antigenemia test is an immunofluorescence-based assay which utilizes an indirect immunofluorescence technique for identifying the pp65 protein of cytomegalovirus in peripheral blood leukocytes. The CMV pp65 assay is widely used for monitoring CMV infection and its response to antiviral treatment in people who are under immunosuppressive therapy and have had renal transplantation surgery, as the antigenemia results are obtained about<unk>  days before the onset of symptomatic CMV disease. The advantage of this assay is the rapidity in providing results in a few hours and that the pp65 antigen determination represents a useful criterion for the physician to initiate antiviral therapy. The major disadvantage of the pp65 assay is that only a limited number of samples can be processed per test batch. CMV should be suspected if a person has symptoms of infectious mononucleosis but has negative test results for mononucleosis and Epstein–Barr virus, or if they show signs of hepatitis, but have negative test results for hepatitis A, B, and C. For best diagnostic results, laboratory tests for CMV antibody should be performed by using paired serum samples. One blood sample should be taken upon suspicion of CMV, and another one taken within 2 weeks. A virus culture can be performed any time the person is symptomatic. Laboratory testing for antibodies to CMV can be performed to determine if a woman has already had CMV infection. However, routine testing of all pregnant women is costly and the need for testing should therefore be evaluated on a case-by-case basis. Serologic testing The enzyme-linked immunosorbent assay (or ELISA) is the most commonly available serologic test for measuring antibody to CMV. The result can be used to determine if acute infection, prior infection, or passively acquired maternal antibody in an infant is present. Other tests include various fluorescence assays, indirect hemagglutination, (PCR) and latex agglutination. An ELISA technique for CMV-specific IgM is available, but may give false-positive results unless steps are taken to remove rheumatoid factor or most of the IgG antibody before the serum sample is tested. Because CMV-specific IgM may be produced in low levels in reactivated CMV infection, its presence is not always indicative of primary infection. Only virus recovered from a target organ, such as the lung, provides unequivocal evidence that the current illness is caused by acquired CMV infection. If serologic tests detect a positive or high titer of IgG, this result should not automatically be interpreted to mean that active CMV infection is present. Active CMV infection is considered to be present if antibody tests of paired serum samples show a fourfold rise in IgG antibody and a significant level of IgM antibody (equal to at least 30% of the IgG value), or if virus is cultured from a urine or throat specimen. Relevance to blood donors Although the risks discussed above are generally low, CMV assays are part of the standard screening for non-directed blood donation (donations not specified for a particular person) in the U.S., the UK and many other countries. CMV-negative donations are then earmarked for transfusion to infants or people who are immunocompromised. Some blood donation centers maintain lists of donors whose blood is CMV negative due to special demands. Relevance to bone marrow donors During allogeneic hematopoietic stem cell transplant, it is generally advised to match the serostatus of donor and recipient. If the recipient is seronegative, a seropositive donor carries a risk of de novo infection. Conversely, a seropositive recipient is at risk of viral reactivation if they receive a transplant from a seronegative donor, losing their innate defenses in the process. In general, the risk is highest for CMV seropositive recipients, in which viral reactivation is a cause of significant morbidity. For these reasons, CMV serologic testing is routine for both bone marrow donors and recipients.
Human betaherpesvirus 5
Human betaherpesvirus 7
Human herpesvirus 6
Trichodysplasia spinulosa polyomavirus
Human T-lymphotropic virus
Oncolytic adenovirus
Human T-lymphotropic virus 1
Yaba monkey tumor virus