A snap lockdown has been declared for the central Victorian city of Ballarat after four COVID cases were confirmed – as authorities warn the state’s outbreak is yet to peak.

Ballarat will begin a seven-day lockdown under the same rules as Melbourne at midnight Wednesday.

It followed confirmed infections in two essential workers and two of their household contacts, as well as multiple exposure sites and wastewater detections in the area.

The workers’ infections were reported on Tuesday, while the household contacts were among 423 Victorian cases reported on Wednesday.

“There are likely to be more cases. We have had positive wastewater detections from the eighth [of September],” Victorian chief health officer Brett Sutton said.

“It’s through all the testing that will happen … tomorrow that we might identify another four, five, 10 community cases. We don’t know for sure.”

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Professor Sutton warned that Victoria, and Melbourne in particular, had not yet reached the peak of its Delta outbreak.

“The modelling and everything we know in relation to our current vaccination coverage would suggest that cases will continue to increase,” he said.

He said while the state’s outbreak “seems to have stabilised” in recent days, “the risk of getting to 1000 is real”.

“We have to press on with vaccinations at the fastest possible rate for that reason alone,” Mr Sutton said.

Melburnians have been promised small extra freedoms – including an extra hour of exercise and an expanded travel limit – once 70 per cent of those eligible have received their first COVID-19 vaccine dose.

That is expected as soon as Thursday, and Premier Daniel Andrews has promised that some rules “might” be relaxed from then.

“We’re not there yet, today is not tomorrow,” he said.

During their seven-day lockdown, Ballarat residents will have to abide by stay-at-home orders with only five reasons to leave home, a ban on visitors at homes and a five-kilometre travel limit. Melbourne’s curfew will not apply in the regional city.

Concern about COVID’s spread outside the cities is not limited to Victoria.

Yass, in NSW’s Southern Tablelands, was sent into a two-week lockdown on Monday after a lone case was detected. In nearby Young, where at least one case has been found, there is speculation it is also facing another snap lockdown.

NSW chief health officer Kerry Chant said the infected person in Young also spent time in Wagga Wagga and Mudgee.

“There is a process if there are cases in towns and we advise on action. We are pulling those pieces together with exposure sites. It is important that everyone in Young follows that public advice, which will be issued locally,” she said on Wednesday.

“There are a number of venues and other urgent testing is being undertaken.”

Victorian authorities will boost testing in Ballarat, and send thousands of extra vaccines to the city. There are already several exposure sites in Ballarat (see them all here).

Professor Sutton said “the great majority of people” in the city had had at least one COVID shot.

“That is a fantastic starting point. If you are not among them, please get amongst them,” he said.

Elsewhere, another regional Victorian city will leave lockdown on Wednesday night. There have been no new coronavirus cases in Shepparton for three days, following a recent outbreak.

“Shepparton has shown us the way – that you can control even the Delta variant even with dozens and dozens of cases if you can quarantine all of those contacts, get very high rates of testing, and drive
vaccination all at the same time,” Professor Sutton said.

Victoria also reported two more virus deaths on Wednesday, taking the toll from its current outbreak to eight.

They were a man in his 70s from Melbourne’s outer-west and one in his 40s from the city’s north.

Victorian authorities have not confirmed if the latter was 46-year-old Martin Blight, who caught the virus after a workplace outbreak, according to the Australian Services Union.

The union confirmed Mr Blight’s death late on Tuesday. It remembered hiim as “a committed ASU member, a father, a friend to many” and said his family wanted everyone to get vaccinated “as soon as possible”.

It’s unclear whether Mr Blight was vaccinated but he had a Pfizer vaccine booked in for September, according to his Facebook page.

-with AAP