With record testing rates which picked up one new coronavirus case, there's "cause for optimism" that South Australia can emerge from its statewide lockdown on schedule next week, Premier Steven Marshall says.
Friday's single new infection came on the back of 23,572 virus swabs on Thursday with SA now three days into its seven-day shutdown.
"It's early days but all of the early indications are positive," Mr Marshall said.
"I think we have cause for optimism, but we've only got cause for optimism because of the great cooperation that we have from the people from South Australia.
"All the early signs are very positive that this will just be a seven-day lockdown."
Chief Public Health Officer Nicola Spurrier said she was also encouraged by the high-testing rates which gave health officials the best chance of picking up any new infections.
"When I see that huge number of tests, it makes me feel reassured that we should be picking up the virus in other parts of the state," she said.
"So that does give me some comfort."
SA's new infection was in a man in his 60s who attended a winery, north of Adelaide, last weekend.
His case took the current outbreak to 15, including eight now linked to the Tenafeate Creek winery near One Tree Hill.
However, Professor Spurrier said the man was already isolating at home in the period when he became infectious and was not considered a risk to the wider community.
A number of other cases in the SA cluster were linked to The Greek restaurant in Adelaide after some infected people attended a birthday party last weekend.
The restaurant and the winery are considered superspreader events.
Mr Marshall said SA would continue to increase its testing capacity with new sites coming on stream, including one to be run by the defence force.
The number of exposure sites has also grown to 79 with the Seppeltsfield Winery in the Barossa Valley and a TAFE college in Adelaide among the latest to join the list.
The growing number of locations has meant thousands of people are now in home quarantine with requirements to have three virus tests.
Some, considered particularly high risk, have also been placed in hotel quarantine.
SA's virus cluster 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 has confirmed the man became infected while in Sydney, not while in Argentina.
Signs of the man's infection may also have been present in wastewater samples checked in Adelaide's northeast last week which returned a positive result last weekend.
Professor Spurrier said it was initially thought the wastewater result involved someone who had previously had an infection, while in hotel quarantine, but was still shedding the virus after release.
"In retrospect...it's likely that the family with this older gentleman was responsible for that positive," she said.
She said wastewater samples from the same catchment, which took in about 100,000 people, had since twice tested negative.
Australian Associated Press