South Australia records another COVID-19 case since reopening borders

South Australia has recorded a new case of COVID-19 after an infected traveller flew in from Sydney.

The person arrived in Adelaide on a Qantas flight from Sydney yesterday morning, meaning everyone who was on the plane must head into isolation for some period of time depending on their vaccination status and location on the plane.

The infection is the third positive test result, and the second infectious COVID-19 case detected in the state since South Australia reopened its borders to the rest of the country on Tuesday.

READ MORE: Young girl is first South Australian COVID-19 case since border reopening

A young Victorian girl become the first South Australian COVID-19 case since the state reopened its borders yesterday after she travelled in by car with her family.

The infectious traveller from Sydney has created a number of exposure sites.

A Victorian traveller also returned a positive result but it was found to be an old infection still shedding the virus.

Anyone who is unvaccinated against COVID-19 and was sitting in rows one to four on the Qantas Flight QF733 from Sydney to Adelaide must get tested immediately and isolate for 14 days.

Any fully vaccinated travellers in those rows must get tested and quarantine for seven days regardless of their test result.

Anyone else who was on the flight at all, or who visited Krispy Kreme between 10.40am and 11.20am yesterday, must get tested for the virus and isolate until they get a negative result.

READ MORE: Jetstar pilot arrested over missing Victorian campers

People who were in Adelaide Airport between 10.15am and 11.25am yesterday, or who were at Brighton Central between 12.45pm and 1.15pm and between 5pm and 5.20pm yesterday, should monitor for symptoms.

Interstate visitors are now allowed to enter South Australia provided they are fully vaccinated and have applied through the EntryCheckSA process.

Quarantine requirements depend on where a person has arrived from.

International visitors or domestic arrivals from areas deemed "high risk" will need to quarantine for seven days.

Most interstate arrivals will need to take a COVID-19 test in the 72 hours prior to arriving in South Australia.

Australian Medical Association SA chief Dr Michelle Atchison yesterday warned it was "too early" for the state to be re-opening its borders.

"There are different numbers floating around but 80 per cent (full vaccination) was the number that we felt was the safest one to open up at," Dr Atchison told Today.

"But unfortunately we are not at 80 per cent, and that leaves pockets of the population particularly vulnerable."

As of yesterday, 78 per cent of the South Australia population was fully vaccinated against COVID-19.