When researchers first identified CMV in the 1950s—the same decade as the chickenpox and measles viruses were discovered—it heralded a golden era of viral research. But whilst this research has led to effective treatments and vaccines that are now routinely used to combat many viral illnesses, research into CMV has often lagged behind. And perhaps most worryingly, only 14 per cent of British women know what CMV is.12
#b04097;">So how is a virus that three in every five people13 have caught at some point in their lives, actually spread?
#b04097;">The main way pregnant women catch CMV is from the urine or saliva of young children
Surprisingly, CMV is not that easily transmitted as it is spread only through close contact with bodily fluids. In fact, the main way pregnant women catch CMV is from the urine or saliva of young children. Younger children pose a greater transmission risk than older children: there are higher levels of virus found in their bodily fluids and they are more likely to spread these around, through drooling, mouthing toys and so on. And the virus can remain present in a child’s bodily fluids for many months or even years after they have recovered from the initial infection.14
CMV can be spread through all bodily fluids—including sexual contact and medical treatments such as blood or organ transplantation—however, saliva is a particular risk. This is because CMV is present at higher levels in saliva than urine. Also, many of the behaviours that increase exposure—such as sharing food and utensils, kissing on the mouth, and wiping the face—are very common practice among mothers and their young children. And these activities also allow for direct transfer of CMV to mucous membranes.
Exposure through contact with urine mainly occurs during nappy changing. However, it is less likely to be transmitted this way than via saliva, as most women say they already clean their hands after a nappy change.15
Aren’t all the people who’ve caught it already immune from it? Unfortunately, people who have already caught CMV do not have guaranteed protection. You can still catch a different strain or have a flare-up of the virus that’s already in your body.
So how does this knowledge of the rather messy transmission of CMV help us? Although there is as yet no vaccine against CMV infection, there is a growing body of research that suggests risks can be reduced.
Research studies from the US, France and Italy have all provided evidence that providing pregnant women with counselling and clear information can reduce the risk of acquiring CMV in pregnancy – in some cases reducing the risk of acquiring CMV by up to 85 per cent.16,17,18 Despite this, information about avoidance of CMV infection is not routinely provided in the NHS.
There is a long history of evidence that educational interventions can prevent congenital diseases. For example, efforts aimed at preventing fetal alcohol syndrome have reduced maternal alcohol consumption in pregnancy,19 prenatal vitamin and folic acid supplementation have lowered rates of neural tube defects,20 and antiviral use in pregnancy has been shown to reduce mother to child transmission of HIV.21
We also know that pregnant women are a highly motivated group who are more likely to follow CMV preventative measures than non-pregnant women,16 and that women
of childbearing age in the UK want to know more about CMV: in a survey of over 1,000 British women aged between 18 and 44, 9 out of 10 (91 per cent) think that pregnant women should be given advice about CMV infection during pregnancy.12 And after reading advice about how to prevent infection, three quarters (75%) of British women of childbearing age think that it is easy to prevent CMV.12
#b04097;">CMV can be prevented.
While we wait for vaccines and other interventions to become available, we have evidence that CMV education may be able to effectively prevent CMV infection in pregnancy. We know that pregnant women want this information and are willing to take appropriate measures to reduce their risk of acquiring CMV infection.
Our immediate priority therefore, should be finding ways in which this education can be effectively delivered to pregnant women in the NHS, at the point at which they most need it.
Professor Paul Heath
Professor of Paediatric Infectious Diseases,
St George’s University Hospitals NHS Foundation Trust