Victorian authorities are worried the state’s latest Delta outbreak may already have spread well beyond Melbourne’s western suburbs.

All of the case in the new outbreak are so far confined to the city’s west.

But recent wastewater detections in bayside Melbourne and Cranbourne, in Melbourne’s south-east, as well as some country areas prompted a warning from the state’s Health Minister, Martin Foley.

“We did not go into lockdown for trivial reasons,” he said.

“We didn’t go into lockdown just because we’re worried about a small number of cases in the western suburbs.

“We’re worried about a Delta penetration again here in Victoria, we’re worried that it might be seeding out quite widely, we’re worried it might be going to places that we haven’t yet seen.

“I know it’s frustrating, I know it’s tedious, but you need to go and get tested if you’ve got any symptoms because that’s the only way that we’ll find it.”

Mr Foley said Victoria was in a “precarious position” on the first full day of its sixth lockdown.

The state had six local COVID cases, including two reported on Thursday. All were linked to previous cases and were in the community while infectious.

Three are relatives of a Hobsons Bay couple aged in their 20s, one of whom is a teacher at Al-Taqwa College in Truganina.

The remaining three cases are linked to a man in his 20s, who lives in the Maribyrnong area and works at a warehouse in Derrimut.

They are a housemate of the man, who is a contracted cleaner at Richmond’s Epworth Hospital, and two contacts from another household in Wyndham Vale, including a student at Warringa Park specialist school in Hoppers Crossing.

The Epworth said the cleaner worked in consulting suites, adjacent to the hospital, and had no contact with patients.

It’s still not known how either the Hobsons Bay couple and the Maribyrnong man contracted the virus, but initial genomic testing has confirmed they have the highly infectious Delta strain.

“It is in all of our hands. We have driven down this Delta variant and we can do it again,” Mr Foley said on Friday.

There are more than 10,000 close contacts of positive cases self-isolating and more than 60 exposure sites across the state. COVID commander Jeroen Weimar said that list would grow.

“We’ll see exposure sites start to spread across wider parts of the city and potentially regional Victoria,” he said.

• See all of the latest Victorian exposure sites here

Virgin flights and terminal three at Tullamarine airport are among exposure sites linked to a positive case who travelled from NSW to Tasmania through Melbourne.

Mr Foley acknowledged “nobody likes lockdowns” but said they would remain a feature of the nation’s public health response until 70 to 80 per cent of the population was vaccinated.

“We can’t rule out their future use but at the moment we’re simply focused on getting ahead of this particular outbreak and avoiding the kind of catastrophe that Sydney and NSW are enduring,” he said.

Mr Foley hoped the state would be able to provide the AstraZeneca COVID-19 vaccine through its hubs for those under 60 who want it by next week. The state government has also called on the Commonwealth to bring forward 150,000 allocated Pfizer doses due to “enormous unmet demand”.

There are six people in hospital battling the virus, including two in intensive care on ventilators.

The seven-day, statewide lockdown took effect at 8pm on Thursday, with the same stay-home rules that applied during July’s lockdown reimposed.

Regional Victoria was included partly because of COVID-19 wastewater detections in Wangaratta, though the local mayor has said subsequent tests came back negative.

Victorians were given less than four hours notice, with authorities keen to avoid a repeat of an outbreak that occurred at a restaurant on the eve of the last lockdown.

A further $400 million will be provided for businesses affected by the latest lockdown.