Health officials say it can't be assumed that SA is now "coronavirus free".

No new infections were reported on Friday, leaving the total 439 with 435 considered recovered.

Four people died from the disease.

Chief Public Health Officer Nicola Spurrier says if SA does get more confirmed cases, they're most likely to come from interstate or overseas.

She says people must continue their efforts to limit any spread of the disease including social distancing and good hygiene.

"If we relax completely, and we don't keep doing social distancing, once we get a couple of cases it will spread incredibly rapidly," she said

"We can see that's happened in other countries, so we all have to continue to play our part."

Premier Steven Marshall said he was excited about the news of no active cases but remains determined not to "take our foot off the brake".

"It's still a disgusting disease, it's still a very nasty disease and thousands of people are still dying," he said.

"We've got to do everything we can to keep everyone safe in South Australia."

Australian Associated Press