"NSW Health determine the sewage testing requirements and have so far not asked for more locations in the shire to be tested," council said.

"Their advice is that testing Eden, Merimbula and Bermagui offers the best shire coverage. We recently received NSW Health permission to increase testing at these locations from once to twice a week as an extra precaution," council said.

The twice weekly testing started on Monday August 16 with samples sent to Sydney Water's West Ryde Lab for analysis.

The results usually come back within two to three days after they are sent, council said.

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"Testing is being conducted across the state right now and the laboratory handling the analysis only has certain capacity," council said.

It was just a week after the increased testing started that COVID virus fragments were detected in the sewage system at Merimbula.

The detection was from a sample taken over August 22-23.

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Bermagui and Eden samples did not return a detection of the virus during the same period and results from the next sample are expected to be available over the coming weekend.