When Victoria Cottrell's son didn't pass his newborn hearing screening tests she thought the reason could be genetic.

Victoria is deaf in one ear and logically assumed hearing loss had been passed onto Teddy, 2, through her genes. 

But a diagnosis of congenital cytomegalovirus (cCMV), the leading cause of infectious hearing loss in babies, caught her off guard.

If it wasn't for a trial being conducted by the Murdoch Children's Research Institute (MCRI) the diagnosis wouldn't have been picked up so quickly and early intervention mightn't have been possible.   

The trial results, published in the Journal of Paediatrics and Child Health, saw parents take saliva swabs from their newborn babies either at home or in a hospital. The swabs were then screened for cCMV, which is not routinely tested for in Australia.

cCMV can be harmless, but in some babies, it leads to hearing loss and neurodevelopmental disorders such as cerebral palsy or vision loss.  About 1 in every 200 babies is born with cCMV. 

Accurate diagnosis of cCMV requires a saliva test from an infant in the first 21 days after birth, with antiviral treatment recommended, if clinically indicated, within the first month of life.

The study found the saliva test was feasible and well-received by families. More than 90 per cent of parents thought the screening was easy to do, was a good idea, and were glad their baby had the test.

Victoria said the test was quick and simple and taking part was the best decision she had ever made.

"I had never heard of cCMV before and thought the cause of the hearing loss most likely was genetic," she said. "During my pregnancy check-ups many infant conditions and foods to steer clear from were mentioned but cCMV was never talked about. The diagnosis came as a shock and was a lot for our family to process."

CMV is present in 80 per cent of Australian adults and while it's mostly harmless, it could affect a developing fetus. Once a person becomes infected, the virus remains present but usually dormant for life. Infection or reactivation can occur during pregnancy, with the small risk that the unborn baby may contract the virus.

"After having Teddy, I was discharged from the hospital within 24 hours, so the second hearing screening wasn't done until a week later," Victoria said. 

"The saliva test results came back only a day before the cut off to start antiviral treatment, so we were really lucky that it was identified in time."                                                         

Teddy underwent six months of antiviral treatments and currently has physiotherapy to help with walking.

Profoundly deaf, Teddy wears cochlear implants and attends programs at Taralye, an early intervention centre for children with hearing loss.

"If his cCMV diagnosis wasn't picked up so soon he would be further behind in his gross motor skills," Victoria said. "Having the awareness early we have received support quickly and our specialists have been on top of everything. "Teddy has grown into a very determined little boy who's curious, loves the outdoors and is always smiling."

Victoria said she would like to see a test for cCMV be added to infant hearing screening programs across Australia.

"If the trial hadn't happened, we would never have known Teddy had cCMV," she said. "I'm just so thankful and relieved that this trial existed to get the best outcomes for Teddy." 

International guidelines recommend targeted cCMV screening of newborns who do not pass their hearing checks.

MCRI Associate Professor Valerie Sung said because cCMV was not routinely screened for in Australia, detecting affected infants in time to offer potential antiviral treatment was less likely.

"Given this saliva test allows for an early and accurate cCMV diagnosis, could reduce unnecessary parental guilt, and help prevent lifelong disabilities it should be rolled out nation-wide through newborn hearing screening programs," she said.

Associate Professor Sung said timely screening for cCMV became more difficult after women and babies were discharged. 

"Early discharge, as we're seeing more now of during COVID-19, can be a big problem because it means we might miss cases of cCMV," she said. "But our study has shown parents can do the swab themselves at home even after leaving the hospital." 

For more on the study, results click here.