The worker at Grant Lodge aged care in Bacchus Marsh was tested on Saturday as part of a Victoria's ongoing screening program, despite being asymptomatic, Djerriwarrh Health Services has confirmed.

"All Grant Lodge staff members who have interacted with the infected staff member are being tested, and sent home for isolation, and the Lodge is in lockdown," they said in a statement.

"Grant Lodge has undergone a complete and thorough cleaning process, and we are currently working through staffing details to ensure residents are being cared for.

"All residents are being tested and their next of kin are being informed."

The new case is just the Moorabool Shire's second confirmed case.

Ballarat's confirmed cases have remained not increased for five consecutive weeks, according to the latest government figures.

Meanwhile, Victoria's Chief Health Officer has hosed down concerns a staff infection early last month was the source for a coronavirus outbreak at a Melbourne meatworks, as more cases have been linked to the abattoir.

Victoria recorded 17 new COVID-19 cases on Wednesday, including four cases from Cedar Meats at Brooklyn in Melbourne's west.

There are now 49 cases linked to the outbreak at the facility.

A worker at a Footscray nursing home who is the partner of one of the meat workers is among those who have tested positive, the Herald Sun has reported.

Chief Health Officer Professor Brett Sutton is confident the outbreak has not stemmed from a worker who tested positive for the virus on April 2, weeks before hundreds of other staff were tested and sent home.

The worker told the Department of Health and Human Services they had not been at the facility for weeks beforehand, ruling out the possibility they could have infected others.

"I have been told that that early case wasn't part of the cluster - wasn't on site," Prof Sutton told 3AW on Wednesday.

Prof Sutton is not aware of anyone informing Cedar Meats of the case.

The second case linked to the workplace was diagnosed on April 24, followed by a third case about 24 hours later. That person had been a patient at Sunshine Hospital for unrelated reasons prior to diagnosis or displaying symptoms.

A healthcare worker became infected through the worker's Sunshine Hospital visit, while others have been quarantined.

It wasn't until April 29 that the department took additional actions, including testing all 350 Cedar Meats staff.

Prof Sutton said it's not clear exactly how the outbreak emerged.

He said reports the worker was confirmed as infected on April 2 and had actually been on site were "a rumour", but could be checked if needed.

The facility has been shut for now and Prof Sutton expects that will bring the outbreak to a head, after some cases emerge in the next two weeks

Agriculture Minister David Littleproud is investigating whether commonwealth officials inspecting abattoirs might have been affected.

"I'm just getting to the bottom of when we were notified because obviously they make an inspection at one abattoir and move to another," he told reporters in Canberra.

"Those commonwealth and department of agriculture personnel who were in that abattoir and then moved to another one potentially could have spread the virus. So I want to get an understanding of what Victorian state officials undertook in that."

Opposition Leader Michael O'Brien said the outbreak was "(Premier) Daniel Andrews own Ruby Princess", referring to the cruise ship that docked in Sydney and is now the subject of a special commission.

"We've now got one of the biggest coronavirus clusters in Victoria because the government has dropped the ball," Mr O'Brien told reporters.

Of Victoria's 17 latest cases, seven are returned overseas travellers who are in mandatory hotel quarantine and six cases remain under investigation.

Eight people remain in hospital, including six in intensive care.

- AAP

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