More than 1.6 million South Australians are today spending their first of six days under a strict new version of a coronavirus lockdown.
They're embarking on what the government is calling a "circuit breaker", to contain an outbreak in the northern suburbs of Adelaide after a six-month stint of no community transmission was broken over the weekend.
It all started with an ominous cough.
Watch: SA today recorded zero new cases. Post continues after video.
On Friday night an 80-year-old woman presented at Adelaide's Lyell McEwin Hospital.
A young doctor on shift that night heard the woman coughing and quickly ordered a test which came back COVID-19 positive by the Saturday morning.
Acting Chief Medical Officer Professor Paul Kelly says it was this quick thinking that was "absolutely essential in picking up that first case".
"The family member that went to that hospital and went to the Emergency Department with something else completely different, no respiratory symptoms, one of the doctors heard that person coughing and did the test and that is how we know that there’s something going on in South Australia very early," he said.
By Sunday, three of the woman's relatives had been confirmed COVID-19 positive.
By Monday the cluster had grown to 17, with 15 of those linked to the one family.
By Tuesday it had swollen to 20.
By Wednesday it was at 23, and today - the first day of lockdown - zero new cases were recorded but SA health is treating 17 suspected cases as cases.
Three people have been hospitalised but are stable, and there are more than 3200 close contacts linked to the Parafield cluster currently being traced.