Ten American tourists and a nine-year-old boy are among 17 new people to test positive for COVID-19 in South Australia today.

Key points: A young boy aged under nine is one of SA's recently-confirmed COVID-19 cases

A young boy aged under nine is one of SA's recently-confirmed COVID-19 cases Another 16 people have tested positive in the state in the past 24 hours

Another 16 people have tested positive in the state in the past 24 hours SA Health's Nicola Spurrier said while the rise in cases is concerning, most are linked to travel at this time

The members of the American tour group tested positive overnight, with a further four members of the 18-strong party awaiting test results.

They will remain in self-isolation at their accommodation.

Seven other new cases have been confirmed in South Australia — the biggest daily increase so far — bringing the state's total to 67 cases.

SA Health's Nicola Spurrier said having such a large number of cases diagnosed in one day was a concern, but said all but three people — whose details were still being investigated — had overseas travel.

"We've had an increase of 17 cases since yesterday in South Australia," she said.

"There's a boy who is less than nine [years old], who has had overseas travel — he's returned from the UK — and he's had no childcare or school exposure."

Along with the young boy, the seven cases unrelated to the American tour group include a woman and a man in their 30s who recently returned from the UK and a male in his 60s who returned from Asia.

Another three people — a female in her 30s, a male in his 50s and a female in her 20s — are still having their details investigated by the SA Health team.

"Then we have a tour group from the US … a male in his 50s, a male in his 60s and a female in her 70s, and the details of the rest of the people from the tour group are still being finalised," Dr Spurrier said.

Dr Nicola Spurrier (centre) announced 17 more coronavirus cases in SA. ( ABC News: Mahalia Carter )

"Overnight, 10 positive tests came through from that group … we are waiting for four of those tests to come back and four people's tests are negative.

"Those people have been assessed this morning with a local GP and one of the nurses from our COVID-19 clinic.

"It's important that we keep that group together, because whilst there are some people whose tests are pending and some whose are negative, it's important that group is cohorted together, because obviously the risk of spread within that group is quite high."

Aged care worker tests positive for COVID-19

Meanwhile, an Adelaide aged care facility also confirmed on Saturday that one of its workers had tested positive.

"St Louis Aged Care was notified by SA Health on Wednesday, March 18, that an allied health worker involved in the treatment of residents at our nursing home in Parkside has since tested positive for COVID-10," the facility's statement read.

"The worker treated residents on Monday, March 16, and was not displaying any symptoms at the time.

"Protocals set by the relevant government and health authorities were immediately implemented upon notification and all residents treated by the allied health worker were isolated to their rooms."

None of the isolated residents are showing symptoms of the virus, but they would continue to be "closely" monitored, the facility said.

Families of residents isolated have been contacted and workers who were in contact with the staff member who tested positive have also been placed into self-isolation for 14 days.

Tour group isolated in hotel facility

Dr Spurrier said authorities had decided to keep the American tour group isolated in their residence at luxury vineyard retreat The Louise, as none needed hospitalisation yet.

"I have to really commend the owners of that residence that they have been doing a fantastic job in being able to help us with this particular issue," she said.

The American tour group is currently self-isolating at The Louise, which is now closed to other visitors. ( ABC News: Sara Tomevska )

"We are now putting in place … measures to monitor them on a daily basis, because of their age.

"We need to make sure there is no deterioration in their clinical status — at the moment, none of them need to be admitted to hospital — but that may change over the coming days and they would be transferred to one of our major metropolitan hospitals."

The hotel released a statement on Saturday afternoon that said from Sunday, "the property and its restaurants Appellation and three75 will close for the next two weeks".

"This short notice and pause in operations comes after the disclosure to management that some current international guests are required to self-isolate after being in contact with a person who has tested positive for COVID-19," the statement read.

"These guests are in need of high-quality isolation and support during this unexpected change in their itinerary, based on the advice of SA Health.

"The Louise has agreed to support these guests in the near term, and will therefore close its normal accommodation and dining venues for the coming two weeks."