Zeroing in on Victoria’s suppression success

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Victoria's achievement in bringing down daily coronavirus numbers from 700 new cases a day in August to none in the past nine days has led Ireland and other European countries to seek our experts' advice on how the state did it.

Introducing measures including a five-kilometre travel limit, an 8pm to 5am curfew, and school and business shutdowns, are now being eyed by northern hemisphere countries as their case numbers climb rapidly.

Victoria’s Chief Health Officer Professor Brett Sutton will host a virtual town hall next week with Ireland to explain how Victoria reduced its coronavirus case numbers so effectively.Credit:Getty

On Sunday, Chief Health Officer Brett Sutton said he had been asked by authorities in Ireland to host a "virtual town hall" next week, which other European countries would join, to learn how Victoria had stemmed its second-wave outbreak.

So what will he tell them? How did we manage to achieve such a steep drop in cases?

"If there are lessons for anyone, it is that it's achievable, and the real benefit is getting to those sustainable low numbers, and using the lessons you've learnt over that period of time to keep them there," Professor Sutton said.

Minimising the huge risk factors in sectors such as aged care – the setting in which almost all of Victoria's 819 COVID-19 deaths have occurred – was another major lesson, he said.

"We've obviously learnt a lot about what the challenging settings were,'' he said. ''Aged care [is] enormously vulnerable, and those amplifying environments of abattoirs and food distribution centres and other warehouse centres with a large working population who are very mobile."

Professor Sutton said Melbourne's lockdown was only one of a range of measures that had helped drive down our tally.

"Stage four restrictions are not the science – that was the tool that was used," he said.

"But the lesson from Melbourne is everything that we did in that time as we drove numbers down. The way that we worked on the turnaround time for pathology testing, the way that we worked on reducing the time for case and contact management and outbreak management, the agent-based modelling that has informed where we get to and how we get there – all of those things were shared with the Health Minister and other public health experts in Ireland."

Premier Daniel Andrews photographed at a COVID-19 news conference on October 28Credit:Joe Armao

"But no one can assume that because … we have had nine days of zero, it is gone and somehow those numbers are the same as a vaccine against this deadly virus. They are not.

"I am really confident that all of the work that has been done to get us here will be maintained and it will keep us in a place where we can continue to open up, have rules that drive more economic activity, more social freedom, a greater connectedness with the people we have missed the most."

Despite the caution, there is the sense that Victoria has witnessed a massive turnaround from just two weeks ago, when many were dismissive of the state’s chances of reaching zero.

Professor Sutton said at the time that Victoria’s last remaining cases had been among “the trickiest in the world” to beat.

But rather than having a "stubborn tail", as Professor Sutton repeatedly described it, Victoria’s epidemic curve shows our highest peak was followed by an equally sharp drop.

The daily number of Victorians who tested positive peaked at 725 on August 5. Two weeks later, the number was down to 208; two weeks after that it was 87.

In the first two weeks of October, the state averaged fewer than 10 cases a day. The first zero day since the second wave was on October 26.

That was driven by dramatic improvements in contact tracing, not just by months of lockdown and mandatory mask wearing, according to Adrian Esterman, a biostatistician at the University of South Australia.

"Victoria has only done what all the other states and territories have been able to do apart from NSW – which is get to zero and keep it there," he said.

Elimination – no circulating virus in Victoria – was a real possibility, he said. But to know it was gone for sure, Professor Esterman wanted to see at least 28 days of zero cases.

Professor Tony Blakely, one of the authors of the modelling that underpinned the Victorian government's virus response, said much of the credit should go to the decision not to reopen from lockdown until cases were averaging five a day or fewer, as well as "top notch contact tracing … and, of course, a good dose of luck".

Dr Jason Thompson, a computational social scientist who built the modelling used by the Victorian government, said his scenarios had showed a sharp drop to elimination, rather than a stubborn tail, was always possible.

“The common wisdom is that it’s not possible,” he said. “The government was saying this was something that was not possible.

“But every time I built a model, we were able to get it down to zero. If you have the controls in place, it will go to zero.”

So long as you can identify, trace and isolate the contacts of an infected person, you can eliminate the virus, Dr Thompson said.

The threat, however, is far from over. The virus continues to circulate in NSW, while leaks from quarantine are a constant threat.

“We will see a resurgence if we have incursions," Dr Thompson said. "You look around the world and the successful countries are island nations or those with tight border controls. We’re not going to have absolutely-impervious borders.”

A high testing rate is another tool that can help show how many cases there are in the community.

Victoria has tested more than 13,500 people a day on average for the past two weeks – more than twice the number in early June, when the seeds of the second wave were planted.

“It means these continuing zero days are giving us a strong signal that we have little undetected virus out there,” said Professor Catherine Bennett, chair of epidemiology at Deakin University.

“Time to switch our focus to prevention strategies to protect this, and step up the sentinel surveillance to catch any last cases that may be out there, and detect new cases as borders open up.”

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