Premier Steven Marshall said on Monday that 94 people were now in hospital, up from 82 on Sunday, with nine of those in intensive care.

The premier also cautioned that cases would continue to rise with the peak of daily infections not likely until later in January.

"We still haven't got anywhere near the peak in our state. We are seeing large surges in other parts of the world, in other parts of the country," Mr Marshall said.

"We don't have a projection in terms of the numbers, but we do have forecasting which will be coming back to us towards the end of the week in regards to what that peak date is likely to be.

"I believe it will certainly be before the end of January."

But the premier said in regards to the Omicron strain of the virus, "nobody has a crystal ball".

"We've been working very hard to make sure we can get on top of it," he said.

"It really has been a very stressful time for the people of our state."

The new virus cases on Monday included that of Opposition Leader Peter Malinauskas who reported feeling well but with minor cold-like symptoms.

He did not indicate how he might have contracted the disease but said his wife Annabel and their three children had all tested negative.

"This is an experience I share right now with thousands of other South Australians," he said in a statement.

"My thoughts are with every South Australian affected by this pandemic, whether it be those who have tested positive, those in isolation, families with holidays ruined, through to those businesses and workers who are grappling with the full impact of restrictions."

Mr Marshall said SA's efforts to slow the spread of the Omicron variant would continue to include putting people into isolation where necessary.

"Nobody wants to get COVID, so putting people who are very, very likely to have it into isolation is the right thing to do," he said.

As such, SA moved to clarify the definition of close contacts which now includes anyone in face-to-face, unmasked indoor contact with a COVID-19 positive case for more than 15 minutes.

The premier said it was very likely that people in those circumstances would test positive for the virus.

The revised definition was in addition to those people who are close contacts as family members or intimate partners or those people considered at higher risk because they attended a specific venue.

All close contacts are required to isolate and get tested.

"This is the final piece of the puzzle, the final piece of advice people have been looking for," Mr Marshall said.

"I think this provides the clarity that people have been seeking."

Australian Associated Press