South Australian health authorities have urged essential travellers considering heading to Victoria to rethink their plans after another COVID-19 case in Adelaide.

Chief Public Health Officer Nicola Spurrier says a man in his 20s who went to Victoria recently and returned to SA on July 26 has tested positive for the virus.

His case follows that of a woman, also in her 20s, who tested positive on Tuesday after relocating from Melbourne to take up a new job.

Professor Spurrier says the two cases show the risk posed by people travelling to Victoria where more than 700 new infections were reported on Thursday.

“There may be people that are seeking essential traveller status so they can go to Victoria and return,” she said.

“But I’m urging all South Australians to think very, very carefully about any need to travel to Victoria at this time.”

Thursday’s new case takes the total number of infections in SA since the start of the pandemic to 449.