South Australian Premier Steven Marshall said coronavirus catastrophe avoided

Modelling has been released by the government showing a catastrophic situation the state could have faced if its virus cluster had gotten out of control.

South Australia has avoided a “catastrophic” situation in the state with one new case linked to a medi-hotel and none linked to the Parafield cluster, Premier Steven Marshall says.

It comes as the state’s Chief Health Officer Professor Nicola Spurrier released the modelling which prompted authorities to shut down the state while contact tracing was “supercharged” to stop a second wave.

The graph shows the reproduction number for the virus had reached “well above” two and potentially was as high as four last week, Professor Spurrier explained.

This meant that one infected person could have spread the virus to two others, or as many as four.

Graph showing the coronavirus epidemic forecast based on inferred date of exposure of cases. Health Department of South Australia.

“Based on that information, we had a 99 per cent chance that the wave that was starting off in South Australia was not going to be just a little blip, but it was going to be a very significant wave,” she said on Sunday.

The reproduction number had previously been sitting at 1.3, she said.

She said the graph showed how quickly the virus would could have spread.

“It shows a forecast of how the virus would spread if we hadn't made the decision to close down and basically supercharge our contact tracing,” Professor Spurrier said.

South Australian Premier Steven Marshall has avoided a catastrophic situation.: Photo Kelly Barnes

Sunday’s new case was woman in her 20s who has returned from overseas and remains in hotel quarantine.

The woman only became symptomatic on day ten of her 14-day quarantine period.

There were no new cases linked to the Parafield cluster in Adelaide’s northern suburbs.

“The consequences of not acting quickly and following that health advice would have been absolutely catastrophic on all businesses, families and individuals in our state in a few moments time,” Premier Steven Marshall said on Sunday.

Testing rates in the state were “phenomenal” with 16,982 coronavirus tests carried out on Saturday, he said.

There was also no sign of any further community transmission from the cluster of 26 people infected with the virus.

A man cycles along the Torrens River in Adelaide after the strict lockdown measures eased. Photo: Kelly Barnes

“I have no regrets on my advice and decision-making last week. I‘ve no doubt it was the right thing to do,” Professor Spurrier said.

Social distancing, mask wearing and getting tested were important to tackling the spread of the virus, she said.

South Australian Chief Public Health Officer Nicola Spurrier has no regrets over her decisions last week. Photo: Kelly Barnes

But the professor said she was “absolutely stoked” with the efforts of South Australians compliance with the rules.

It comes after South Australia’s lockdown ended at midnight, three days earlier than planned.

But the Premier had earlier said the state was not out of the woods yet with one new virus case confirmed on Saturday linked to the Parafield cluster.