Premier Steven Marshall says the result is a "huge relief" and will allow the week-long shutdown to end at one minute past midnight on Wednesday.

He says it vindicates the state's "go hard and go early" approach to combating virus clusters.

"So a massive thank you to everybody. We acknowledge how tough this week has been," he said.

"We don't put these restrictions in place lightly, but if we didn't we would be in a very different situation."

When the lockdown lifts, SA will keep a range of heightened restrictions including a general density requirement of one person to every four square metres.

Masks must be worn in high-risk settings, such as aged care centres and personal care services, in medical services, on public transport and in all indoor public places, including supermarkets.

The wider use of masks is strongly encouraged, including in workplaces.

All food and drink consumption must be seated and dancing and singing remain banned.

Family gatherings will be limited to 10 people, although weddings and funerals can have up to 50.

Schools will reopen on Wednesday and secondary students will also be required to wear masks.

Sports training can resume, but competitions will be delayed until August 7.

The new restrictions will remain in place for at least a week.

Chief Public Health Officer Nicola Spurrier said SA still had about 6000 people in home quarantine and it was important for them to complete the full 14 days.

She said once the lockdown ends, the general rule with mask use should be "if you can wear a mask, wear a mask".

The shop assistants' union welcomed mask-wearing for the retail sector where it said workers "put themselves at risk for our communities".

"With retail outlets and shopping centres making up nearly half of the exposure sites in South Australia and over 80 of exposure sites in the NSW outbreak, mandatory mask-wearing in these settings acts as a baseline defence against this virus," the union said.

But it said mask-wearing was not a foolproof defence and workers faced other issues such as non-compliant and abusive customers.

Police Commissioner Grant Stevens said based on his own observations and feedback from his frontline officers, South Australians deserved a "10 out of 10" score for their response to the lockdown.

"It's something the community should be incredibly proud of. We got through this difficult time," he said.

"It happens because everybody did their part in minimising the potential for this virus to spread."

Mr Stevens said he was absolutely certain SA did the right thing in moving to a rapid shutdown last week.

"The decision was sound and based on strong evidence and advice," he said.

"We only have to look over the border to see the consequences of not taking a hard-line approach very early."

During the lockdown, police issued 256 fines for breaches of COVID-19 directions and issued another 455 cautions.

With no new cases, SA's Modbury cluster of coronavirus cases stands at 19 confirmed infections, with 11 of those linked to the Tenafeate Creek winery near One Tree Hill.

It began with an 81-year-old man who recently arrived in Australia from Argentina and was quarantined in Sydney before travelling to Adelaide, where he tested positive.

Genomic testing confirmed the man became infected while in Sydney, not while he was in Argentina.

Overall, SA has 25 active COVID-19 cases, with the other six related to returned overseas travellers.

Two people are in hospital, both in a stable condition.

Australian Associated Press