Local health authorities are on alert after the man's infection was confirmed, with 12 exposure sites confirmed.

Victorians could return to tighter COVID-19 restrictions if evidence emerges that the man infected others in the community.

But the man, listed as an interstate acquired case, was the only infection in Wednesday's health department update.

It means Victoria has gone 75 days without a local case.

The department is awaiting the results of genomic testing to confirm how the man was infected.

Victorian Health Minister Martin Foley will give an update on Wednesday morning.

Mr Foley also expressed disappointment the federal budget did not provide direct funding for a quarantine facility that Victoria wants to build north of Melbourne.

The man, in his 30s, flew into Adelaide from India via the Maldives and Singapore on April 19 before Australia's flight ban on returnees from India began.

After completing quarantine in South Australia at the Playford Hotel, he returned to his home in suburban Melbourne's Wollert early last week and developed symptoms on Saturday before testing positive on Tuesday.

SA authorities are examining whether the man contracted the virus before his arrival and had an unusually long incubation period, or caught it from a person in a neighbouring hotel room.

Victoria's Chief Health Officer Brett Sutton suspects the man picked it up in the hotel, and not in India or during his international flights.

All three of the man's household contacts have tested negative, with Professor Sutton describing this as an "early encouraging sign".

Contact tracers have identified four "tier one" exposure sites linked to the man, including an Altona North office where he worked and an Indian restaurant and bar in central Melbourne.

Anyone who visited the sites at specific times must get tested and isolate for 14 days from exposure.

Two Friday night train services to and from Craigieburn and Southern Cross are among five "tier two" exposure sites.

The domestic flight and Adelaide and Melbourne airports are not among the exposure sites as the man isn't believed to have been infectious at the time.

But Victoria's COVID-19 response commander Jeroen Weimar said the health department was contacting passengers through the flight manifest, asking them to take a precautionary test.

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He added that evidence of community spread within Melbourne would prompt officials to consider "the next set of appropriate measures".

"I'm not going to sit here and speculate on what that might be," he told ABC Melbourne radio.

"If we are finding positive cases in the workplace or exposure sites that would obviously be a significant cause for concern."

Mr Weimar said it appeared not all of the 30 to 40 diners in the Curry Vault restaurant on Friday night checked in with the Services Victoria QR code system.

SA's genomic sequencing report could shed light on the source of the man's infection but is expected to take 48 hours to complete.

Meanwhile, Mr Foley renewed the state government's call for the commonwealth to provide $200 million for a quarantine facility at Mickleham, north of Melbourne.

"We're very disappointed that the commonwealth hasn't stumped up, it would appear, to help get us through the global pandemic, keeping our borders safe," he told ABC Radio.

"Victoria and all the states have stepped in to make sure hotel quarantine is delivered."

Prime Minister Scott Morrison said earlier on Wednesday the Victorian proposal was "very comprehensive" and that his government was working on it with the state government.

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