What Do The Blood Test Readings For The Cytomegalovirus Mean?

When checking blood for the cytomegalovirus there are two listings — one for the IgG and one for the IgM levels. What’s the difference? And what does it mean if the IgG is as high as 35.0 when I’m told that positive is anything over 0.7? 35.0 seems extremely high to me but the doctor says it’s nothing to worry about.

Cytomegalovirus (CMV), is a member of the herpes virus family that includes the two well-known herpes viruses, I and II, the chickenpox virus (VZA), the Epstein-Barr virus (EBV), and several others. All of these viruses very commonly infect humans, and all have the property of persisting for our lifetimes once we have been infected. EBV, perhaps the most common of all of them, is found in 90 percent of adults throughout the world. It causes infectious mononucleosis when we catch it as an adolescent or young adult, and in everyone the virus periodically reactivates and is excreted through saliva. Hence the name “the kissing disease”, since it is most efficiently transmitted though contact with the saliva of someone who is excreting it.

CMV infects us less frequently than EBV but is still common, with estimates that about 40 percent of adults have been infected. When an adolescent or adult is first infected with the virus, it may produce symptoms indistinguishable from infectious mononucleosis. The syndrome can produce the same fever, fatigue, muscle aches, enlarged spleen and liver inflammation that is typically seen in mono caused by EBV. Sore throat and enlarged glands are less common than in mono due to EBV. Blood tests may be necessary to distinguish between the two infections. Mono caused by EBV one year, and mono caused by CMV a few years later, probably led to the mistaken belief that the original mono recurred, or that the person caught a new EBV infection.

Once one has gotten over the mono, CMV remains latent in most people for the rest of their lives, although they may excrete virus from time to time and thus infect others. Virus has been found in saliva, breast milk, feces, urine, vaginal secretions and semen. Sexual transmission among young adults is thought to be a major mode of infection. It is not clear where the virus hides after one has gotten over the original infection.

If a pregnant woman is infected by CMV for the first time, the infection can be transmitted to her fetus and cause fetal death or birth defects. About 5 percent of infected newborn infants can get a severe infection called cytomegalic inclusion disease, but the great majority of infected infants develop no symptoms of disease.

Other than newborns, the group that is at risk for severe CMV infection is people with severe immune deficiency, either because of medications given to persons receiving organ transplants, or for chemotherapy, or people infected with HIV. Those receiving organ transplants can experience a recurrence of a CMV infection that they had long before, or can catch CMV from the transplanted organ if the donor had it. There is now an attempt with some transplants to match the CMV status of the donor and the recipient, to avoid infecting a previously uninfected recipient.

People with AIDS can have several types of recurrent CMV infection, the most common being a retinitis, or infection of the retina of the eye, which can lead to blindness if untreated. This is never seen in people with intact immune systems.

You ask about the meaning of two types of test for CMV, the IgG and the IgM levels. IgG and IgM refer to different types of antibodies, the proteins produced by our immune system when we have some kinds of infection. IgM antibodies do not persist in the blood for more than a few months. Therefore, a high level of these indicates a recent infection. IgG antibodies persist often for a person’s lifetime, and therefore indicate that the person had the infection at some time, but it could have been many years ago. I would interpret your high IgG level as indicating an infection in the past, and I agree with your doctor that it poses no danger to you now, and never will unless you require cancer chemotherapy or a transplant, or you are infected with HIV.

The information provided on Health Search Online is for educational purposes only and is not a substitute for medical advice, diagnosis or treatment.