South Australia health authorities have ordered the temporary shutdown of Thebarton Senior College in Adelaide's inner-west and 1100 students and staff who attend the college to self-isolate after a new case of coronavirus was reported late on Thursday.

SA chief public health officer Dr Nicola Spurrier said at a late press conference on Thursday that a woman in her 20s had tested positive. She has also ordered 70 students deemed as ''close contacts'' of a previous case connected with the college to go into immediate quarantine at a ''medi-hotel'' in Adelaide.