State leaders are increasingly concerned people might become complacent about the risk of coronavirus as case numbers fall across Australia.
Victoria recorded just 13 new cases on Wednesday and four more deaths.
Melbourne's 14-day rolling average of cases has dropped to 16.4.
Workers in high-risk industries will be randomly tested for coronavirus as Victoria slowly eases restrictions.
Businesses in the meat processing, supermarket and distribution will need to organise tests for 25 per cent of their staff each week.
Victorian aged care workers will also undergo regular testing.
"This thing can simmer, it can be out there and not necessarily be obvious to you," Victorian Premier Daniel Andrews told reporters on Wednesday.
NSW has recorded four new cases of coronavirus, all of whom are returned overseas travellers in hotel quarantine.
The state has gone five straight days with no locally acquired cases.
Premier Gladys Berejiklian is worried people enjoying the school holidays are becoming less cautious about social distancing.
"We know that the threat of the virus lurking in our existing community is already high ... so I don't want anyone to be surprised if tomorrow, the day after, we do get cases of community transmission," she said.
Meanwhile, Queensland has opened up to 150,000 extra NSW residents in 41 postcodes in its border bubble.
Premier Annastacia Palaszczuk said the reopening would be a huge relief for locals and businesses, but stopped short of committing to any time frame on a full border reopening.
Queensland recorded another day of no new cases and there are just five active infections across the state.
"It's great to see what's happening in NSW ... but once again, NSW health advice is saying very clearly they are concerned about the mass movement of people during school holidays. So we're going to watch that very very carefully over the coming weeks," Ms Palaszczuk said.
South Australia's transition committee will meet on Thursday to consider easing more COVID-19 restrictions amid growing calls for relief across a number of business sectors.
SA reported no new coronavirus cases on Wednesday and has no active infections.
Meanwhile, WA has raised concerns about potential outbreaks triggered by ship crews granted onshore changeovers.
WA authorities have scrambled to contain an outbreak of 17 cases on the Patricia Oldendorff bulk carrier anchored off the Port Hedland coast.
None are seriously unwell.
"Quite clearly there is a major issue looming as we are now moving into the eighth or ninth month of the COVID pandemic," WA Ports Minister Alannah MacTiernan said.
"I think there's going to have to be a lot of examination and international co-operation as to how we deal with this."
Australian Defence Force personnel will arrive in WA on Thursday to help police and security guards oversee the hotel quarantine.