A 1-year-old baby and two children are being treated for the deadly disease after their family became embroiled in South Australia's worst cluster to date.
South Australia continues to grapple with the beginning stages of a second wave after its coronavirus cases jumped again.
There are now 20 cases linked to the Parafield family cluster with three cases being treated as active but yet to be confirmed by health authorities.
The family cluster includes three young children, one of whom is 1, Premier Steven Marshall confirmed this morning.
Overall the state recorded 18 new Covid-19 cases yesterday and one new case this morning, for a total of 35 active cases, including hotel quarantine cases.
Four of the 34 active cases are employees at the Anglicare Brompton Aged Care Home in Adelaide, which the CEO of Anglicare SA this morning described as his "worst nightmare".
All residents have so far tested negative, however, CEO Peter Sandeman said they would be tested again tomorrow and any close contacts were being isolated.
SA Health is continuing to study the genomic strains of each of the state's new cases, which will help them determine who caught the infection first.
A female cleaner in her 50s, working at one of Adelaide's medi-hotels named Peppers, is believed to have caught it first, later inadvertently passing it on to family and two unrelated hotel security guards.
While the results will be subject to further scrutiny, it comes after Pfizer announced its candidate was also 90 per cent effective, potentially giving the world two vaccine options to choose from.
'Worst nightmare': Four aged care employees now positive
Four aged care employees – all from the same aged care home in Adelaide – have now tested positive to coronavirus.
"We are in full PPE and we've been testing all the residents and I'm pleased to say all the residents have tested negative at this stage. We will retest tomorrow," Sandeman said.
The two nurses who initially tested positive were a mother and daughter from the large Parafield family cluster.
Sandeman told the programme that two more staff from Brompton Aged Care Home were part of the cluster of 20 cases that has rocked Adelaide.
"Unfortunately two more staff have subsequently tested positive and are in medi-hotel and isolated and of course we're testing all staff as they turn up for work," he said.
"Four staff who have been working shifts have tested positive, that's correct."
Sandeman described it as the "worst nightmare any aged care proprietor can face".
"The residents are holding up well. The staff are all caring for the residents but progressively, of course, we will have to replace staff as staff are assessed as a risk."
South Australia's health department enforces a policy of immediately moving any aged care resident to hospital if they test positive for coronavirus.
"That's a major risk mitigation strategy that's in place in South Australia that wasn't elsewhere," Sandeman said.
The Anglicare Bromptom Aged Care Home is a facility for homeless people, with Sandeman saying there was a "great deal of affection and trust" between residents and staff.
Sandeman said the staff were being "very strong" and "holding up considerably well".
Every Adelaide flight grilled upon arrival to Melbourne
Authorised officers are at Melbourne's Tullamarine Airport today, interviewing every passenger who disembarks from Adelaide.
The officers will interview each passenger before assessing their risk of infection.