South Australia has recorded four new cases of COVID-19 – including one “unlinked” case in the Port Noarlunga region – prompting an urgent call for testing in Adelaide’s south.

In an update late on Friday, SA Health said three men aged 20-70, and one woman in her 30s, had tested positive for COVID-19.

All of the new cases are fully vaccinated.

Two are interstate travellers, while one is linked to the growing Norwood cluster – the source of 16 cases on Thursday.

SA Health also said one case has been classified as “unlinked” due to a “yet unknown source of infection”.

The case has spent time in the Port Noarlunga region in Adelaide’s south, according to SA Health.

“People in the Onkaparinga LGA, including Port Noarlunga and Reynella, who have any symptoms of COVID-19, are strongly encouraged to seek testing with any symptoms whatsoever, and isolate until they receive a negative test result,” SA Health said in a statement.

“SA Health is working to increase capacity in testing sites in this area.”

The state’s COVID-19 tally since the borders reopened on November 23 is at 35 cases, with 31 active.

Tweet from @SAHealth

It comes after Western Australian Premier Mark McGowan moved overnight to ban South Australian travellers from entering WA after 18 new COVID-19 cases on Thursday – 16 linked to a Henley High School reunion in Norwood last weekend.

The other two cases on Thursday were acquired interstate.

As of Friday morning, more than 200 people in South Australia were in quarantine, with about 150 of those linked to the Norwood cluster, according to the state government.

Earlier, Premier Steven Marshall said he expected more cases to pop up.

“I’m sure there’ll be some more cases today, that was always going to happen when we opened our borders,” Mr Marshall told ABC Radio on Friday.

“We’re certainty managing those numbers, and I think we’re managing those numbers extremely well at the moment.”

On Friday, SA Health listed COVID-19 exposure sites in Marion, Blanchetown and Gawler East.

The highest risk location, according to SA Health, is the Goodlife Health Club in Marion, which has been deemed a close contact exposure site.

Anyone fully vaccinated who was at the gym on Tuesday, November 30, from 7.20-8.30am is required to get tested immediately and quarantine for seven days, while unvaccinated contacts are asked to quarantine for 14 days.

The Blanchetown Deli Takeaway and Hardware has been listed as a casual contact exposure site for Monday, November 29, from 3-5pm, with a quarantine until negative test order in place for contacts.

The Gawler Health Service in Gawler East has been listed as a low-risk casual contact location for Tuesday, November 30, from 8.45-6pm.

SA Health also listed exposure locations in Adelaide’s West overnight, after issuing alerts on Wednesday for sites in Adelaide’s inner east and southern suburbs.

It came as Mr Marshall defends the state government’s decision to reopen to fully vaccinated travellers from NSW, Victoria and the ACT, despite calls to reverse the decision.

He said WA’s move to close the border was disappointing for South Australian travellers.

“I think that was inevitable to be quite honest,” he said.

“They’ve had a different approach over in Western Australia to the national cabinet agreed position.

“It’s obviously disappointing for people that are here wanting to go into Western Australia, that’s now not going to be able to proceed.”

Defending South Australia’s timetable for reopening, Mr Marshall said that he “feel(s) for anybody that is going to be dislocated from friends and families and business opportunities in Western Australia” but emphasised “that was the decision that was made by the Western Australian government, not ours”.

He also rejected suggestions he had overruled advice from SA Health calling to close South Australia’s borders again.

“To be quite honest, the numbers in regards to Norwood have got absolutely nothing to do with state borders,” he said.

“We said that from the time that we got to 80 per cent with the fully vaccinated population 16 and over that we would end statewide lockouts and lockdowns.

“Our thinking was based upon the Delta variant, we’ve got a new variant now – that’s the thing that concerns us the most, certainly not the numbers around the Norwood cluster.”

He said it was still “too early to say” whether the Omicron variant would prompt any further restrictions, but noted authorities were concerned about quarantine times for international arrivals in Victoria and NSW.

Currently, international arrivals in the two eastern states are required to quarantine for only 72 hours, compared to 14 days in South Australia.

“We will look very very carefully at those numbers interstate, and also, as we gather more information regarding the severity of [Omicron’s] symptoms, we’ll make decisions to protect our population,” Mr Marshall said.

“But at this stage, we’re just monitoring it very closely.”

On Friday, NSW Health reported its ninth confirmed case of the Omicron variant – a student in Western Sydney – and expressed concern the infection is a case of community transmission.

“NSW Health is concerned the virus may have been acquired in the community as the case has no overseas travel history or links to people with overseas travel history,” a spokesperson said.

NSW had 337 virus cases on Friday – its highest daily tally in six weeks – although no new deaths were recorded. Victoria had 1188 cases and 11 deaths.

As of Wednesday, 80.9 per cent of people in South Australia over the age of 12 are fully vaccinated.

-With AAP

• This story was first published in InDaily and is republished here with permission