Rent relief will be given to South Australian business tenants and reductions will be provided to landlords under new state government schemes.

Rent relief will be provided to South Australian tenants of commercial, retail, industrial and non-residential businesses that were forced to close due to COVID-19.

As part of the state government's $1 billion economic stimulus package, tenants will have a reprieve from their forced closure date or when they were significantly impacted until June 30.

Infrastructure Minister Stephan Knoll said businesses would save about $4.5 million.

"For some businesses this means they could be saving tens of thousands of dollars which they can use to help pay bills, employ staff and help keep their doors open," he said.

The state government is also offering about $50 million in emergency land tax relief to landlords to assist residential and small and medium-sized businesses, like gyms, cafes and beauty salons, with rent reductions.

Under the program, land owners will be offered a 25 per cent reduction on the 2019-20 land tax liability on affected properties.

The scheme applies to non-residential tenants with an annual turnover of up to $50 million that experience a minimum 30 per cent income reduction due to COVID-19.

Applications will be accepted until the end of June.

Meanwhile, health officials have thrown their support behind a contact tracking phone app set to be rolled out.

Chief Public Health Officer Nicola Spurrier said the app would be "incredibly helpful" to her staff's efforts to track down people who may have come in contact with the virus.

The app is expected to be introduced in the next few weeks with the data to only be made available to state health officials for their work to combat COVID-19.

So far SA has had 438 confirmed coronavirus cases with none reported on Thursday.

Of those, 394 people, or 90 per cent, are now considered recovered and only 40 active cases remain.

Four people are still in hospital with two in a critical condition in intensive care.

As part of its two-week blitz, SA Health also conducted a further 1675 tests on Wednesday, taking the total since February to more than 48,000.