People who take PCR tests will now be told whether they have flu or respiratory syncytial virus (RSV) in addition to their result for Covid-19.
Public Health Wales, in conjunction with the Welsh Government, said the change will help improve surveillance of winter respiratory viruses.
Those who test positive for either flu or RSV will receive a text message, separately to their coronavirus result text, informing them of the result. The change will be rolled out from this month.
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This new testing regime will only apply to tests carried out in NHS Wales labs and not those that go through lighthouse labs.
Dr Robin Howe, national clinical lead for microbiology at Public Health Wales, said: "The platforms that are used to test samples for coronavirus can also test for a number of viruses including flu and RSV. This enables us to monitor the spread of these viruses through the winter in Wales.
"Giving people the confirmation that they have flu or RSV rather than Covid-19 will mean that they are able to access the care that they need more easily as well as protecting other people by staying away from them."
Respiratory syncytial virus (RSV) is common in babies and children under two years old with cases typically peaking around January.
While most will only have mild symptoms which can be looked after safely at home the condition can cause severe breathing issues and hospitalisations if it develops into bronchiolitis – a chest infection that affects the smaller airways of the lungs.
Some parts of Wales have seen an increase in cases of RSV, including Aneurin Bevan University Health Board which stated on January 12: "In recent days we've seen increasing numbers of RSV patients coming through our doors.
"This is a very common virus in children under two years old. Most children will develop RSV in the first year of their life and will display mild cold symptoms. However some children will become more unwell and may need hospital treatment.
"You should see your GP if your baby is taking less than half of their usual feeds or is working hard to breathe. If your baby's tongue or lips are blue or they are having severe difficulty breathing you should dial 999 immediately or go straight to hospital."
Incidents of flu have also increased across Welsh communities this winter when compared to 12 months ago. There have been concerns about the low take-up of the nasal spray flu vaccine among two and three-year-olds in some parts of Wales.
Walk-in clinics for the nasal spray vaccine were held in all five of Cwm Taf Morgannwg's community vaccination centres earlier this month.
Advice on the action to be taken following a positive flu or RSV result can be provided by accessing the advice from Public Health Wales at www.phw.nhs.wales/FLUtestresult or www.phw.nhs.wales/RSVtestresult
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