The key number in Victoria’s COVID-19 cases that has experts worried

The staggering number of new COVID-19 cases in Victoria – 191 yesterday and 134 today – are bad, but another figure is even more alarming.

Melbourne will be plunged into a six-week lockdown following yesterday’s news of another surge of coronavirus – but it’s not the figure of 191 new cases in a day that worries experts.

Eighty per cent of the infections recorded on Tuesday, or 154, are being classified as ‘under investigation’ – meaning health authorities aren’t sure of the source of the spread.

Today, another 134 cases were confirmed and of those, 123 also can’t be immediately traced.

It’s a sign of potentially widespread community transmission, which has now been described as “a runaway train”, and adds to a growing trend observed in recent weeks.

Community transmission is a much more complex problem to tackle and will make Victoria’s second wave a bigger challenge than the first outbreak in March, Professor Adrian Esterman, a biostatistics expert and epidemiologist from the University of South Australia, explained.

“The thing is, cases that we know about and can trace, we can isolate those infected and do contact tracing, and basically close the transmission and stop it from spreading,” Prof Esterman said.

“It’s difficult for authorities to work out where the infection has come from. If you can’t do that, it means there are more cases out there.”

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The situation in Victoria is grave and the rate of community transmission is a “runaway train”. Picture: Getty Images

Melbourne will be shut down for six weeks as a result of the worrying resurgence of coronavirus in Victoria. Picture: Ian Currie

Of the 2824 total cases of COVID-19 recorded in Victoria, infectious disease experts believe 438 are the result of community transmission.

Dr Alex Polyakov, a senior lecturer at the University of Melbourne and consultant at Royal Women’s Hospital, said those rates are cause for alarm.

“Once community transmission takes hold, it is almost impossible to control the spread with the currently implemented measures,” Dr Polyakov said.

Cases in hotel quarantine versus in the community: gross new daily cases. Picture: Covid19data.com.au

Transmission sources of new daily cases. Picture: Covid19data.com.au

The situation in Victoria is “grave” and locking down the capital and state’s northern border might not be enough to prevent a spread to other states, Professor Raina MacIntyre, head of the Biosecurity Program at the Kirby Institute at the University of NSW, said.

It’s probably too late, Professor MacIntyre said, and the detection of new outbreaks in New South Wales and other states within the next few weeks is likely.

“It is possible there has been seeding of infection to other states, and silent epidemic growth which has not yet being detected,” she said.

“The situation we are in is more serious that late March, because we have community transmission, which is much harder to track than infection in return travellers.”

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That stark reality likely gave Premier Daniel Andrews no choice but to shut down the Greater Melbourne region, home to almost five million people, to get on top of the spread.

Will it be enough? Experts are divided.

“Lockdowns and movement restrictions will only be partially effective and further actions are required to minimise the spread of the virus,” Dr Polyakov said.

“In my opinion, the most effective, and so far largely neglected strategy, is universal wearing of masks in public.

“This should be implemented immediately and will certainly enhance the current strategies.”

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Daniel Andrews says re-entering lockdown was the last thing he wanted but the spread of coronavirus was “unsustainable”. Picture: Ian Currie

Infectious disease specialist Professor Marylouise McLaws from UNSW, who is on the World Health Organisation’s COVID-19 committee, also fears yesterday’s lockdown call might’ve come too late.

“It’s like a runaway train,” Prof McLaws told The Sydney Morning Herald. “We’ve got to act pretty proactively to stop that.”

Mr Andrews conceded the situation has become “unsustainable” and the surge in infections meant there weren’t enough health workers to conduct contact tracing.

During the lockdown, he said large-scale testing efforts will continue and confirmed the total number of coronavirus tests conducted has passed 1 million.

“We did 29,424 tests yesterday, so substantially higher than the records we had set earlier in the week,” Mr Andrews said.

But the hardest task is still to be confronted – another long period of lockdown that will hurt businesses and the community alike.

“We are all working as hard as we can, doing the very best that we can, and we know that we’re asking a lot of Victorians,” the premier said.

“We didn’t want to be in the position that we are in, but that’s the reality that we confront. This is the challenge that we have to meet and I think that if we all work together over these next six weeks, as painful and frustrating and difficult as that will be, we will be able to get to the other side of this stay-at-home period.”

The border between Victoria and New South Wales is shut from today. Picture: AFP

Perhaps the only piece of good news is that the Victorian health system is well-prepared for a potential influx of patients.

One thing is for certain – the resurgence of the virus is likely to get much worse before it gets better, experts say.

Professor Paul Glasziou is the director of the Institute for Evidence Based Healthcare at Bond University and said the long incubation period of COVID-19 means the end of this new wave of cases and illness will take some time to make themselves known.

“We should expect a lag of 5-10 days before numbers drop substantially, and a few weeks before good control returns,” he said.