Chief Public Health Officer Nicola Spurrier said the person had since returned two negative tests suggesting the first result may have been a false positive.

However, she said out of an abundance of caution, the five close contacts would isolate for 14 days.

They have all returned negative results with SA posting no new virus cases on Monday.

Professor Spurrier said it was possible the man who travelled to NSW had previously come into contact with COVID-19 positive truck drivers who recently travelled into SA.

Also on Monday, the state's transition committee eased rules around dancing and stand-up drinking in licensed venues despite the changes cutting across health advice.

Police Commissioner Grant Stevens said it had been decided that dancing could return from Thursday at private functions where attendance limits are set at 150 people.

The number of people allowed on the dancefloor will also be restricted to 50.

Mr Stevens said stand-up drinking would also be allowed in outdoor areas in pubs and clubs from Thursday.

He said the changes went against advice from Professor Spurrier but he believed they balanced the risks with the level of frustration within the SA community and the desire to ease coronavirus measures.

"It's about managing the balancing the risk. We've done exceptionally well in South Australia," he said.

"If we do have concerns in relation to seeding from other places into South Australia, these things that we're announcing now are the first things that will come off the table.

"We are at a point where it is very difficult to find concessions that we can make without substantially increasing risk."

In other changes, SA will scrap travel restrictions on people coming from the greater Brisbane area from Saturday.

They will no longer need to have a coronavirus test on arrival but must still fill in a cross-border application.

Australian Associated Press