Cytomegalovirus (CMV): Common and Confusing
Saturday, September 23, 2006
Kenneth F. Trofatter, Jr., MD, PhD
CMV is the MOST common congenitally (fetal) and perinatally (newborn) acquired virus disease in humans and the single most important infectious cause of mental retardation and congenital deafness in the U.S. and other industrialized nations. CMV is a member of the herpes family and human CMV is restricted to humans with no known animal reservoir. At least 80-90% of individuals are infected with CMV during their lives, but infection may occur in the absence of overt disease or the recognition that an illness is the result of CMV. As with other herpes viruses, once an individual is infected with CMV, periodic 'recurrences' can result from reactivation of virus replication at various sites in which the virus is latently harbored in the body. Although probably not that common, secondary infections can also occur with other strains of CMV. No cross-reactive immunity is afforded by previous infections with other herpes viruses such as herpes simplex, varicella-zoster (chickenpox), or Epstein-Barr (mononucleosis) viruses.
Transmission of the virus can occur from exposure to just about any body fluid, most commonly via saliva, respiratory, and venereal routes or by contact with infected urine or breast milk. Exposure tends to occur at earlier ages in lower socioeconomic groups, promiscuous individuals, and children at day care centers. Serologic evidence (seropositivity) of infection in women during the common childbearing years (18-35) is about 50% for those in middle and upper, and 90% in lower, socioeconomic groups. Among seronegative women, the chance of infection (seroconversion) is about 1-3% per year, however, this is as high 10-20% in women who work in day care settings and 50% in women with infected children under two years of age!
Congenital infections with CMV occur in 1-2% of ALL pregnancies meaning the virus can cross the placenta with relative ease compared to other herpes and most other common virus infections. But, as we shall see later on, congenital infection rarely results in the poor outcome noted above unless the congenital infection is the result of a primary (first time) infection in the mother during the pregnancy. Neonatal infections are commonly acquired by exposure to an infected genitourinary tract during delivery, breast milk, and saliva of family members. Infection of the newborn rarely has the serious consequences that are seen with congenital infections resulting from primary maternal disease during the pregnancy. Serious but, generally not life-threatening, neonatal infections can result under the rare situation in which primary maternal infection occurs late in the pregnancy and delivery occurs before the mother has developed immunity to the virus that could be passed along to the fetus in utero.
As a baseline, a relatively constant percentage (10-15%) of seropositive women is found to be excreting CMV from the urinary tract at any given time. The incidence of excretion tends to increase throughout pregnancy with cervical rates in the third trimester as high as 35-40%! Overall, among seronegative women, there is about a 0.5-1% risk of a primary CMV infection in each pregnancy, although this is much higher in 'at risk' groups such as day care workers, health care providers, and women with young children. Pregnancy does not appear to increase the risk of contracting CMV, nor does it place the woman at greater risk for more severe primary infections. There is some evidence though that women who do develop more severe infections (CMV mononucleosis) and those women with asymptomatic infections who are at greatest risk for transmitting the virus to their babies have qualitatively different antibody responses to CMV than women who do not.
In the next post we will look at the spectrum of maternal and fetal disease caused by CMV...
14 Comments:
At Fri Oct 19, 02:27:00 PM 2007,
cassidy mcfarland said…
I am a mother who has recently suffered the loss of a child who suffered severely from problem due to congential cmv. I was infected with the virus during my pregnancy but was unaware of it. The virus is so terrible that it caused my son to have a CVA during utero and my son suffered from being deaf, blind and he also had torticolis. I am very interested in this nasty virus, any more information that you put up here is deffinately well needed and well appreciated. Do you know any good sites to do more research on the virus?
At Mon Oct 22, 04:35:00 PM 2007,
Kenneth F. Trofatter, Jr., MD, PhD said…
Hi Cassidy: I am so sorry for your son's problems. It is truly a devastating virus when you catch it for the first time during pregnancy. Many folks do not even know they have gotten the infection. The Center for Disease Control has a very informative site on CMV. You can get to it by following this link: http://www.cdc.gov/cmv/
Fortunately, it is VERY unlikely another child of yours will be affected in this way, so best of luck and thank you for reading. Dr T
At Thu Nov 15, 05:59:00 PM 2007,
Anonymous said…
I have had reoccurring miscarriages and my OB did a TORCH? blood test which showed my CMV levels were slightly elevated. I’m supposed to go back in two weeks for another test to recheck the levels. Could this virus have caused my miscarriages? Is there a period of time I should wait before trying to conceive again? If I do become pregnant again am I at risk of having a baby affected by CMV?
At Sun Nov 18, 07:30:00 PM 2007,
Kenneth F. Trofatter, Jr., MD, PhD said…
To Anonymous Nov 15: I devoted a full reprise post to CMV because of your interest today, November 18,2007. Your questions are answered there! Thanks for reading and for the incentive to revisit this important subject! Dr T
At Fri Nov 23, 12:20:00 PM 2007,
Anonymous said…
I want to say thank you for your response. You provided me with some much needed answers.
Thanks again,
Anonymous Nov 15th
At Thu Nov 29, 04:52:00 PM 2007,
Kenneth F. Trofatter, Jr., MD, PhD said…
To Anonymous Nov 23: You are welcome. Glad I could help. Thanks again for reading! Dr T
At Mon Mar 10, 10:45:00 PM 2008,
Anonymous said…
I gave birth to three children. My middle child was born in 1985. I contracted CMV during my pregnancy with her and she was born profoundly retarded with calcifications of the brain, etc. She passed away at 9 months old and only after that, did the doctors tell me she probably wouldn't have lived to reach the age of five. The horror that I wen't through due to her death, you don't want to know. But I can tell you that the baby girl I gave birth to 2 years later is perfectly fine. Pregnant women should not touch litter boxes, change babies without washing your hands(even if it's your own) or listen to doctors when your telling them your sick and they do nothing. You are in control and if you have experienced a tragedy like I have, don't worry. You should be immune now should you get pregnant again. If you lost a child from this wicked disease, don't worry. I think they all are together with whatever God you believe in. Thanks, keep the faith, it isn't you!
At Fri Mar 14, 03:11:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To Anonymous Mar 10: Thank you so much for sharing your story with us. It is heart-breaking, but you have given justifiable hope to other women who are in similar circumstances. Thank you for reading and best wishes. Dr T
At Sun Mar 16, 02:44:00 AM 2008,
Anonymous said…
Hi,
I am an pediatric ICU RN and before becoming pregnant (approx. 3+ months) was assured that I was seropositive for CMV. I am now 26 weeks pregnant and just found out that one of my patients that I cared for last week (approx. 25 weeks pregnant) tested positive for CMV (he is immunocomprimised and is on Cytovene). What are the chances of my baby becoming reinfected with the disease? Should I be concerned?
Thank you!
At Fri Mar 21, 07:06:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To anonymous Mar 16: Sorry it has taken so long to write. Since you are CMV positive, you are more liekely to be a source of infection of your baby (about 1-2% chance) than any CMV infected children to which you are exposed. However, since your exposure to CMV occurred prior to the pregnancy, the overwhelming odds are that your baby will be protected from the more severe manifestations of congenital CMV. You can have your baby's urine tested shortly after birth for CMV and if it is positive, then your pediatrician will usually simply follow with periodic assessment of growth, development, hearing and vision - things they follow anyway! Good luck to you and let us know how things turn out. Dr T
At Thu Apr 17, 06:46:00 PM 2008,
Anonymous said…
My daughter is a special education teacher with the severely disabled. She is 7 weeks pregnant and just learned that one of her students is CMV positive. This student contracted CMV during his mother's pregnancy and is severely mentally retarded. My daughter just received results on her CMV testing and it shows she has the antibodies or has been exposed. She goes back in 3 weeks for another blood test. Her OB/GYN has recommended she have no contact with the student or the classroom due to the fact the student drools and my daughter often has open wounds due to bites, scratches, etc. from the students. The school district is somewhat hesitant to "reassign" her to another classroom. We understand that good sanitary precautions help but are very fearful of her contracting a recurring CMV infection. Can you offer advice please???? You can email me at jslone9628@aol.com thanks so much for your blog and time.
At Sun Apr 20, 06:49:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To anonymous Apr 17: Your daughter probably has PRIOR immunity from her years of working in special ed and this will probably protect her baby. Many nbabies in special ed are chronic excreters of CMV. Regardless, she needs to use good handwashing techniques and should probably wear gloves when she has to handle this child. There are other strains of CMV and there is variable cross-reactive immunity. She and her baby will probably do just fine. See my comment above yours for some insight into her risks from reactivation of her own CMV. These too are small. Please let us know how things turn out. Dr T
At Wed Jul 09, 06:40:00 PM 2008,
Anonymous said…
I have been around kids a vast majority of my life. My mom ran a daycare many years ago. I then chose to be a nanny, Applied behavioral analysis provider for children 0-3, and am now a service coordinator for children with disabilities from 0-3. A coworker of mine said that she contracted CMV for the first time in her first trimester and suggests that any of us get tested to ensure that we've already had CMV. Our company makes us sign a policy stating that we're aware that we may be exposed to CMV and are not responsible for our exposure. I am a little paranoid given that I miscarried last year (for reasons I'm sure are not from CMV). I read that the tests to see if one has CMV can be inaccurate. Should I and can I assume that at some point I've already been exposed to CMV?
At Sat Jul 12, 07:57:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To anonymous July 9: I think you should have the test done. They are not inaccurate. They can tell you if you have been exposed to and therefore have CMV. Sometimes they are difficult to interpret, but if you have CMV-specific IgG, you will at least know you are immune and a baby should be protected as much as possible. Dr T
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