It comes as new cases were this morning announced in New South Wales and Queensland, while lockdowns or tight restrictions have been imposed in four states as the highly contagious Delta strain sweeps the country.

South Australian officials are set to announce a series of new internal restrictions at a 1pm press conference, after the state yesterday slammed its border shut to Queensland, WA, the NT and the ACT, after previously locking out travellers from NSW.

Chief public health officer Professor Nicola Spurrier told FIVEaa that the new restrictions were needed to prevent the spread of the Delta strain should it make its way across the state’s border.

“We’re looking at masks, we’re looking at reducing the density in hospitality, but to a level that hopefully would have minimal impact to our economy,” she said.

“I know it’s going to hurt some businesses, but this is going to be for a short period of time and it’s in response to the fact that we’ve got very serious outbreaks not just in one state but in many states now around Australia.”

Spurrier told ABC Radio Adelaide that if the Delta strain made its way to South Australia, an infectious person would pass the virus on to three and a half other people.

“The plan is today to put some restrictions in place that try to bring that number down a little bit,” she said.

“It just puts a little bit of a dampener on things in case we do get a case here.”

Spurrier said authorities were “mindful of balancing the social and economic impacts” when imposing new restrictions and there was “no intention to have this on for a long period of time”.

“What I’ve done with the team is go through all the different things that can help stop the transmission of this awful, nasty disease and look at the ones that will not have too much economic impact,” she said.

“It will be for a short period of time as those other states work very, very hard to get on top of their outbreaks.”

She said that aged care restrictions could also be reimposed, while SA Health would have conversations with Adelaide Oval ahead of next weekend’s AFL round.

Meanwhile, SA Health revealed 29 workers from a Northern Territory mine where a worker tested positive for coronavirus were in South Australia.

The worker at the Granites mine, which is 540-kilometres north-west of Alice Springs, tested positive on Friday after about 900 fly-in fly-out workers had left the site to return to their homes across Australia.

We can only move as quickly as we’ve got the information

Workers in South Australia have been tested and asked to quarantine at their home with their families for 14 days.

“When I went home last night we had results back from 11 of those people – they were all negative,” Spurrier said.

“I haven’t had any bad news on my phone this morning – I’m sure some of those results will have come in overnight and we’ll be collating that this morning.”

Spurrier said SA Health contacted the 29 workers “very early yesterday morning” and she wasn’t “too concerned” about them being out in the community before isolating.

“Obviously, it’s all a concern, but we can only move as quickly as we’ve got the information,” she said.

Prime Minister Scott Morrison has called a meeting of the national security committee of federal cabinet to discuss the outbreaks.

He will also bring together state and territory leaders for a national cabinet meeting on Monday evening.

Morrison is expected to push state and territory leaders to make vaccines mandatory for aged care workers.

National cabinet will also discuss quarantine practices, including a ban on accommodating low-risk domestic travellers next door to high-risk international arrivals, which triggered an outbreak in Queensland.

They will also discuss testing and vaccinating those directly and indirectly working in the system, and introducing post-quarantine testing on day 16 after people emerge from isolation.

Vaccine stocks and the national rollout will be canvassed, along with federal supports available for aged care responses and pandemic disaster leave payments.

For South Australia, we’re actually in a relatively good position

NSW recorded 18 new local coronavirus cases today, with all but one linked to existing cases.

The outbreak, which has grown to 130 cases since June 16, has prompted Greater Sydney to enter a 14-day lockdown.

Queensland is reintroducing restrictions after recording two new locally acquired cased of coronavirus.

Masks will be mandatory across large swathes of the state, home visits will be capped at 30 guests and venues will need to adhere to a one person per square metre rule.

In the Northern Territory, the outbreak linked to the Granites mine has grown to six cases, while in Western Australia, a woman who returned from Sydney has picked up the virus, prompting increased restrictions including indoor mask use.

The outbreaks have prompted a multitude of border tightening measures, including South Australia’s closure to all jurisdictions except Victoria and Tasmania.

However, Victorians now need to be tested for the virus on the first day they arrive in SA.

“For South Australia, we’re actually in a relatively good position,” Spurrier said.

“We are one of only a couple of states and jurisdictions in Australia where there is not a current outbreak, but people would have known if they are following the news that there is a very, very significant outbreak now in New South Wales of the Delta strain and it has shown itself to transmit between people extremely quickly (and) extremely easily.”

– with AAP