Melbourne is on edge as the threat of another coronavirus lockdown looms amid fears a growing outbreak will develop into a deadly third wave of the virus.
On Wednesday, Dr Stephen Parnis, who works in emergency departments across three of the city's biggest hospitals, said the next 24 hours were "absolutely critical" to control the 15-case cluster.
"The second wave occurred because it had gotten away from us at this time last year, before we even knew it," Dr Parnis told A Current Affair last night.
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"(This time) it's a matter of understanding the scope of exposure and spread across mainly Melbourne, but we also know there have been instances outside of Melbourne as well."
There are fears the virus may already have found a path interstate, as NSW Health urgently contacts people from a sporting club who attended an event in Victoria where one of the new confirmed cases of COVID-19 was present.
Victoria's Acting Premier James Merlino said "further action" could not be ruled out if the Whittlesea cluster continued to grow.
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New restrictions are already in force across Greater Melbourne, including mandatory mask-wearing and limits on private and public gatherings.
"We'll update people as soon as we know," Mr Merlino said.
"These cases so far are all linked, and that's a good thing, but we are concerned about the number (of cases) and the kind of exposure sites."
Exposure sites grow
AFL matches are still expected to go ahead with crowds despite the new outbreak already being linked to two games last weekend and one interstate match being postponed this coming Saturday.
Marvel Stadium and the MCG are both listed as COVID-19 exposure sites after two matches on Sunday.
Mr Merlino said any matches going ahead would be subject to restrictions, including mask rules.
Victorian Chief Health Officer Brett Sutton said possible lockdown restrictions would hinge on further review of the newest cases.
Health officials have identified 301 primary close contacts.
Professor Sutton said it was a "concern" there had "been exposures over a number of days".
Some of the cluster cases are known to have been infectious and out in the community for more than a week.
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How Melbourne's COVID-19 cases are connected
Case one: Man in his 30s got tested on Sunday.
Case two: Man in his 70s who went with case one to get tested.
Case three + four: woman in her 70s and child, detected after being deemed close contacts.
Case five: Had a business meeting with case one.
Cases six-nine: Same family unit as case five, but different households.
Cases 10-12: Workplace contacts of case nine. The workplace is a finance firm in Port Melbourne.
Case 13: Another contact of case one.
Cases 14-15: Workplace contacts of case nine.
