This article waslast modified on 12 February 2018.

Infection with cytomegalovirus (CMV) causes few symptoms in most people. More than half of UK adults have been infected while children or teenagers. As with other herpes-type viruses, CMV will remain inactive in their bodies for life unless they develop a weakened immune system, for example following HIV infection.

If a woman becomes infected with CMV for the first time just before or during pregnancy, there is a possibility that she may pass the infection on to her unborn baby, a condition known as congenital CMV. About one in ten babies infected in this way have problems at birth including prematurity, lung, liver and spleen disorders and fits. Nine out of ten of babies with problems at birth and some of those who are born with congenital CMV but who have no symptoms at birth will experience problems that develop over their first few years of life. These include hearing loss, visual impairment, blindness, learning difficulties and epilepsy.

A CMV screening test for all babies at birth would allow those who are infected but symptomless to be identified and monitored so that appropriate intervention could be provided. A standard test for congenital CMV is rapid culture of a saliva specimen obtained at birth. However, culture cannot be automated so it is not suitable for screening large numbers. An alternative is to detect the DNA of the virus in saliva using a rapid polymerase chain reaction (PCR) that does not need extraction of the DNA. This method can be automated.

The New England Journal of Medicine of 2 June 2011 reported a multicentre screening study of CMV in newborns funded by the US National Institute on Deafness and Other Communication Disorders. The authors compared the rapid culture of saliva specimens obtained at birth both with real-time PCR assay of liquid saliva specimens and, for the first time, with PCR assay of saliva specimens dried on filter paper. The last method would allow specimens to be sent to a specialist automated screening laboratory for rapid testing as is done with the dried heel prick blood spots used in the current UK National Newborn Screening Programme.

The US study screened 17,662 newborns with both culture and the liquid saliva PCR assay. Of these 17,569 had negative and 85 positive results by both assays. It also screened 17,327 newborns by both culture and the dried saliva PCR assay. Of these 76 were positive by culture while 74 were positive by the dried saliva assay. Taking rapid culture as the 'gold standard', liquid saliva PCR correctly identified 100% of those with CMV and correctly excluded 99.9% of those without CMV. Dried saliva PCR correctly identified 97.4% of those with CMV and correctly excluded 99.9% of those without it. The authors concluded that both PCR assays should be considered potential screening tools for CMV in the newborn. (However, ideally several years follow-up of the nearly 35,000 babies negative by all three tests are needed to determine the true positive rate.)

The current policy of the UK National Screening Committee that screening for congenital CMV should not be offered has been under review since March 2011. It is estimated that the review will be completed by March 2012.