Victoria will close its border with South Australia for 48 hours from midnight Thursday (AEDT).

Meanwhile, NSW Health is asking people entering from South Australia, by whatever mode of transport, to complete a declaration form.

Victorian Premier Daniel Andrews said the “hard border” would be in place for 48 hours from 11.59pm on Thursday and be replaced by a permit system from Sunday.

The decision comes after fragments of the coronavirus were detected in untreated wastewater taken from Victoria’s Benalla and Portland treatment plants on Tuesday.

The preliminary positive test results, which were received on Thursday, were “unexpected and concerning”, as no residents of either area – Portland in Victoria’s south-west and Benalla in the state’s north – are known to have had a recent coronavirus illness or diagnosis.

Under the hard border, only freight drivers and those with medical or emergency reasons, urgent animal welfare or legally authorised will be able to cross the border.

“This was an appropriate thing for us to do and it’ll be difficult in those next couple of days,” Mr Andrews said on Thursday.

“Once the permit system is up and running, it’ll be a little easier and it will be in place no longer than it needs to be.”

Mr Andrews urged residents of Benalla and Portland, as well as anyone who visited either town between November 15-17 with “any symptoms at all” to get tested and to isolate until they get their result.

Deputy chief health officer Allen Cheng said Victoria’s permit system would reflect the strict lockdown measures in South Australia.

“You can come over the border from South Australia to Victoria if you are permitted to leave your home in South Australia,” he said.

The permit system is still being developed, but reasons to enter Victoria will include shopping for essential supplies, receiving medical care, and performing agricultural or essential work.

Tweet from @SAHealth

South Australia, which began a stringent six-day lockdown on Thursday, had no new COVID cases. Its troubling Parafield cluster remains at 23 infections, although the state also has a further 17 suspected infections.

There were 12,000 virus tests conducted across the state on Wednesday. More than 3200 people remain in quarantine in SA as it tries to stamp out the outbreak.

Premier Steven Marshall said the statewide shutdown remained absolutely necessary to break the chains of transmission and prevent more widespread community infection.

“The lessons of surging infections in Victoria and other parts of the world have been learnt,” Mr Marshall said.

“Indecision plays into the hands of this virus.

Victoria recorded its 20th consecutive day with no coronavirus cases or deaths on Thursday.

There are three active cases in the state, with 17,161 people tested in the previous 24 hours.

Tweet from @SAHealth

NSW to relax rules for New Year’s Eve festivities

NSW Premier Gladys Berejiklian says special health orders will be introduced in her state to allow for New Year’s Eve celebrations.

Choirs of up to 30 people will be allowed to perform at carols by candlelight events.

Ms Berejiklian said up to 3000 people would be able to attend outdoor events on New Year’s Eve, as long as the events met specific COVID guidelines. That will include audience members wearing masks.

There were no locally acquired coronavirus cases in NSW in the 24 hours to 8pm Wednesday.

It means there has not been a locally acquired case in the state for 12 days.

There were five infections among returned travellers in hotel quarantine.

Ms Berejiklian announced the relaxation of rules to allow people to organise their Christmas and New Year’s Eve celebrations.

“Even though we’re easing these restrictions as one-offs, it doesn’t reduce how contagious the virus is or how concerned we might be if suddenly an outbreak consumed a large number of people in a particular location,” she said.

“This can only work if all of us stick together and do the right thing.”

On New Year’s Eve, anyone visiting friends or family who live in Sydney’s CBD will have to have a permit.

In other rules announced on Thursday, events with allocated seating will allow one person per two square metres, while those where people are sitting on picnic rugs will have to meet the four-square-metre rule.

The capacity of outdoor church services will increase from 300 to 500 people.

From December 1, capacity at funerals will increase to 300 people.

Ms Berejiklian said she was keeping a “watching brief” on the situation but was considering a further winding back of restrictions.

Warning for arrivals from South Australia

NSW’s chief health officer Kerry Chant urged anyone who had recently returned from South Australia to monitor for symptoms and get tested if they appeared.

Tweet from @NSWHealth

She said contact tracers had been in touch with recent arrivals, prompting them to check South Australia’s health website to determine whether they could be a close contact of a case.

Dr Chant also said anyone coming from SA must fill out a new declaration form designed to remind them if they had been in any venues of concern and to allow NSW Health rapid access to their contact details.

-with agencies