Two active COVID infections were recorded in the City of Ballarat at the weekend: one on Sunday was linked to the existing three households in the outbreak; one on Saturday was linked to a known exposure site in Melbourne.

Of Ballarat's 12 positive cases, all are isolating with in-home care and none are in the city's north.

Grampians Public Health Unit's Aaron Bloch said this was a "mixed picture" for Ballarat, which remains in lockdown at least until Thursday.

"We know we've got three main households and we haven't had any significant spread outside of that, so that's really positive and bodes well for us," Dr Bloch said.

"But on the other hand we are still seeing more cases such as the one last night with more potential links to Melbourne and we are still seeing on Friday night a wastewater detection, so we have to assume still there is still undetected COVID in the community."

Grampians Public Health Unit continues to work with the new case reported on Sunday, both for care needs and to identify relevant Ballarat exposure sites.

Dr Bloch and Ballarat Health Services acting chief Melanie Robertson reiterated on Sunday the importance of the community turning up for COVID testing in a bid to uncover all virus in the community and to improve the city's chances to come out of lockdown sooner.

About 3600 people turned up for a COVID test in Ballarat on Friday and this number halved on Saturday.

Dr Bloch urged the community to keep getting tested, even if for reassurance, to help build vital knowledge for health authorities. He said every negative test helped to build a strong picture of what Ballarat was facing.

Anyone who has visited an exposure site must get tested and isolate. Dr Bloch expected more sites to be added for Ballarat in coming days and he said it was vital people keep monitoring these sites and to be proactive in seeking a test rather than wait for a test message notification from an overwhelmed health department.

IN OTHER NEWS

Residents in towns north of Ballarat, such as Creswick, are urged to be on alert after significant spikes for COVID fragments were reported in wastewater overnight on Friday.

About 80 per cent of wastewater within City of Ballarat goes to the Ballarat South catchment while Ballarat North includes collection part of the Hepburn Shire, which is not in lockdown.

Grampians Public Health Unit medical director Rosemary Aldrich, speaking to media on Saturday, said the detection still needed to be subject to the usual investigation process but this was similar to how the Ballarat outbreak starts. She said, like Ballarat South detections, where there was smoke there was usually fire.

People who are double-vaccinated must also get tested with symptoms because they can still catch and spread the virus.

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