“I’m quietly hopeful we are tracking well, our case numbers continue to trend downwards,” she said.
“It’s important we don’t become complacent.”
Only six people remain in hospital with the virus, with two people in ICU.
Health authorities believe it will be weeks before the impact of the Black Lives Matter rally held on Saturday will start to show in the COVID-19 tally.
A massive crowd flocked to State Parliament in Melbourne to join the global wave of protests sparked by the killing of African-American man George Floyd by police officers in the US city of Minneapolis on May 25.
Dr van Diemen said that when people gather in large numbers and the Health Department does not receive contact details for potential tracing of the virus, it “does present a risk, and not an insignificant risk”.
“In terms of a potential outbreak, it will be at least a week or closer to two weeks before we know there’s any transmissions as a result of that (demonstration). Please get tested if you have any symptoms,” she said.
Lord mayor Sally Capp told 3AW while she was pleased Saturday’s major protest was “peaceful and respectful”, it would be “disappointing” if Victorians had to wait longer for measures to loosen due to another outbreak.
She said health authorities are closely watching the number of COVID-19 infections to inform exactly when restrictions are rolled back.
“We must keep prioritising the health response, and the protest should not have gone ahead,” Cr Capp said on Sunday morning.
She said if no COVID-19 cases are connected to the protest, the mass gathering could “possibly” be used to lift restrictions sooner because it would show there are low levels of the virus in the community.
“But I don’t think it was worth the risk, in terms of the mass rally yesterday,” she said.
But Dr van Diemen said while it might be the lord mayor’s “opinion” that a cluster from the protest would mean restrictions would be lifted slower, the Health Department had a “clear project of works looking forward, and there’s a number of different factors” when considering future action.
“A very large, widespread community outbreak is one of them, whether it is related to a rally or not,” she said.
“We remain vigilant across all cases, regardless of what their source might be. Obviously if there are a large number of cases, then that will make our jobs slightly more difficult, but we remain very much focused on finding every case and tracing every case.”