Targeted coronavirus testing is being considered in Swansea and Neath Port Talbot in response to growing cases.
But there are currently "no immediate" plans to follow in Merthyr Tydfil's footsteps and roll out mass testing.
Last week data showed that Neath Port Talbot had the highest coronavirus case rate in Wales, with one in four testing positive for the virus
Now, the county borough has the second highest cases per 100,000 people, at 770 for the period of December 3-9 after it was overtaken by Merthyr Tydfil, just three weeks after mass testing took place there.
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Swansea currently has the fifth highest rate of cases per 100,000, at 667, with Newport and Bridgend also ahead of it.
In a joint statement issued by Neath Port Talbot Council and Swansea Bay University Health Board, they said the impact of mass testing in Merthyr Tydfil was being studied, but that testing smaller communities was more likely to happen.
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The statement said: “There are no immediate plans to roll out whole community testing in Neath Port Talbot or indeed across the Swansea Bay University Health Board area.
"Testing in targeted communities is however being discussed in a number of forums.
"Currently, an initial evaluation of the Merthyr pilot has now been received and is being studied and considered.
"The Merthyr pilot was in an area with a population about a sixth of the Swansea Bay Health Board area and half the size of Neath Port Talbot County Borough.”
