Victoria’s COVID-19 target not achievable, experts say
Experts have weighed in on Victoria’s road map out of lockdown, with some fearing the targets set will be impossible to reach. It comes as new Melbourne research shows the “magic number” for keeping the virus in check.
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Disease experts have declared Victoria’s tough zero coronavirus targets “unattainable”, saying the state had locked in an “all or nothing” road out of lockdown.
Epidemiologists told the Herald Sun the government’s threshold for a “COVID normal” — 28 days without new cases — was “potentially unworkable” and “unattainable”.
Professor Mary Louise McLaws, an epidemiologist at the University of New South Wales and adviser to the World Health Organisation on health emergencies, said eliminating the virus would be hard.
“If you can keep the number of cases down to less than five cases over a 14-day average, what you have is the ability to find every contact — therefore you’re in a safe place,” she said.
“But the idea of requiring zero (cases) for 28 days is very stringent and potentially unworkable, because 18 to 20 per cent of cases will be asymptomatic.
“That means there will always be potentially some community spread.”
She said strict contact tracing and a national strategy which focuses on being “pre-emptive, rather than reactionary”, was needed.
Deakin University’s chair in epidemiology Catherine Bennett said she was disappointed the government had solely considered an “all or nothing” approach.
“No one anticipated no restrictions, we know we have to chart a safe course out,” Prof Bennett said.
“But why wouldn’t they have compared different scenarios … regional Victoria only needs to get there with regional Victoria’s numbers, but Melbourne can only move beyond this step when all of Victoria is at less than five — why this discrepancy?”
Epidemiologist Peter Collignon, of the Australian National University, said the government’s plan was outright “unattainable”.
He said an elimination strategy was a bad plan and Victoria’s contact tracing system would make it near-impossible to achieve.
“Some of their criteria (for ending the lockdown) is less than five cases in two weeks with no known source,” he said.
“But if you look at the Victorian figures, they have still got huge numbers of undefined cases.”
The experts spoke out after Monash University modelling showed a “magic number” for containing outbreaks.
The research analysed the effectiveness of COVID-19 controls across China and found that the early stages of containment were crucial to how the virus spreads.
It showed that once the total number of cases reached 30, there was a significantly higher chance of cases rising “off the charts”.
But if kept below 30, public health systems could cope and cases could be controlled.
Associate Professor Lei Zhang said the modelling would be important to how Victoria managed outbreaks in coming weeks as numbers continue to trend down.
“It appears that 30 means a loss of control by authorities on the spread of the virus,” Prof Zhang, an epidemiologist from the university’s central clinical school, said.
“At 30, we can manage contact tracing and stay-at-home (orders), but once it rises above 30 there’s a lot of community transmission going on in the background and the authorities lose control.”
Researchers also found the average time between case numbers increasing from 30 to 100 was 6.6 days, but depended on the strength of contact tracing and containment efforts.
Prof Zhang said it was possible that Victoria could be better off with a more relaxed strategy and a tightening of quarantine measures for positive cases.
He said face masks would become our best defence, with between 70 and 90 per cent compliance needed to “maintain a certain advantage”.
The research, a collaboration with the China-Australia Joint Research Center for Infectious Diseases at Xi’an Jiaotong University, analysed data from 436 Chinese cities between January and March.
Researchers also looked at data from Hubei province, including the epicentre of Wuhan and subsequent waves, which showed similar trends when attempting virus control.
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