This outbreak, as was the case with the cluster that exploded to monumental proportions in Victoria earlier this year, has been linked to a returning traveller quarantining in a "medi-hotel".

That person passed it on to a worker who, in turn, passed it on to other members of their "large family". From there the virus spread with remarkable speed, according to South Australia's chief public health officer, Dr Nicola Spurrier. "We just kept getting positives coming off the machine," she said.

The key difference between the outbreak in Adelaide and Victoria is the speed and strength of the responses from both the South Australian and federal governments. As soon as it was known the virus was active in the community for the first time in many months authorities hit the panic button.

Schools, restaurants, and a supermarket have already been closed down for deep cleaning; additional testing stations have been established; hundreds of people who may have come in contact with the growing number of infected people are now self-isolating; and the federal government was quick to offer South Australia the assistance of the defence force.

Financial support is being offered to people without sick leave who may need to self-quarantine and anyone who displays any symptoms whatsoever are being urged to get tested.

"You must get tested the day you get symptoms - you are not to go to work... this just leads to a flow-on effect of a chain of transmission where more and more people can get infected," Dr Ferrier said.

It seems extremely unlikely, given the South Australian premier Steven Marshall was quick to impose fresh restrictions on public gatherings, pubs, clubs and restaurants, gyms, funerals, community sport, and church services yesterday, that this is going to be allowed to fester unmonitored and uncontained until the state is in the grip of a genuine second wave.

One of the most heartening developments has been the response of the community with thousands of people presenting for testing all across Adelaide on Monday and, at this early stage, little or no blowback over the restrictions that have been reintroduced.

Australia is, in effect, seeing a pressure test of its tweaked and changed COVID-19 responses, including contact tracing, in the wake of Victoria's second wave crisis. And, while it is far too early to say how this will ultimately turn out, it does seem fair to say that when it comes to contact tracing the South Australians are doing a good job. They were able to track down and test dozens of people who may have been exposed to the virus within 24 hours of the first positive results coming back.

And, while some will criticise as over-the-top the response by some states and territories to declare South Australia a hot spot and to close down only recently re-opened borders, nobody can blame individual chief ministers and premiers for acting in the best interests of their own residents.

The Victorian experience, which culminated in the virtual elimination of the virus in that state, was an object lesson in the extreme measures that have to be taken to eliminate a second wave once it gets out of hand.

While that very serious situation was ultimately brought to an end without the disastrous effects seen in other parts of the world, it was a cautionary experience for all Australians.