Victoria’s coronavirus infection rate appears to be trending downwards in an encouraging sign Melburnians are complying with restrictions.
Although it is much too early to celebrate, the declining growth rate offers a glimmer of hope to Victorians that their sacrifices are paying off.
On Monday, the state recorded 322 new coronavirus cases, the state’s lowest tally in 13 days. There were also 19 deaths, a record high.
The data, compiled by covid19data.com.au, shows Victoria’s growth rate of active coronavirus cases as a seven-day average dropped below one on August 9, for the first time since the state’s second wave began.
Sure, but what does that actually mean?
Before Stage 3 restrictions were reintroduced in parts of Melbourne in early July, the reproduction rate of the virus was 1.75.
This meant that for every 10 people who had the virus, a further 17 or 18 people were getting infected.
But now the infection rate has dipped below one, it means each individual case is not spreading to multiple people.
Professor Marylouise McLaws, an infectious diseases expert at the University of NSW and member of the World Health Organisation’s COVID-19 response team, said the data supported her findings.
She said Victoria’s infection rate started to plateau in late July and was “definitely declining” in the first week of August.
We need to congratulate Victorians for co-operating because it’s showing up in the numbers,’’ Professor McLaws said.
“They need to continue to co-operate, but they do need to be congratulated.”
However, she also warned Victorians should prepare for fluctuations in the coming weeks.
“It is good news, but don’t be perturbed if there is a bump in the road every so often,” she said.
“Don’t get a little disappointed, especially as death rates go up.”
Victorians must remain vigilant, however, by sticking to the rules and wearing face masks when in public or sharing rides.
“Don’t let your guard down, because this virus will use that,” she said.
Numbers don’t lie, but neither do they tell whole story
Forecasting the future of COVID-19 – a new and unpredictable virus – is a challenging task.
Another spike could occur at any moment.
Dr Paul Vella, a Victorian data scientist, said it appeared the decline in growth started about the same time Melbourne had 10 postcodes locked down in early July.
“This tells me the decline is driven by the lockdown measures – and they are working,” he said.
However, he added the data chart was “slightly misleading”.
“Because the virus spreads person to person, and because we have such a large population not exposed [unlike Italy, Spain or the UK], any single outbreak has the potential to result in many new cases,” Dr Vella said.
“As we’ve seen with outbreaks in Victoria and NSW, all it takes is one person not following the rules for a resurgence in cases.”
The danger of super-spreaders and hotspot postcodes
Dr Daswin De Silva, deputy director of La Trobe University’s Centre for Data Analytics and Cognition, agreed that Victorians could be “cautiously optimistic”.
But he also pointed out the state’s reproduction number was “almost zero just before the quarantine hotel outbreak began”.
“Another obvious – but also critical factor – that this method does not account for, is super-spreaders,” Dr De Silva said.
If the reproduction number is two, normally one person would infect two people maximum.
But this is not the case for super-spreaders, he said.
All it takes is for one super-spreader – a highly infectious person who might not even know they are sick – to visit multiple cafes or pubs in one day for a major outbreak to occur.
Another piece of information the data does not show is the virus’s reproduction rate in different postcodes.
“There is possibly a clear divide in the R-value for the south or eastern suburbs,” Dr De Silva said.
“In some areas, it could be above one. That’s the curse of an average.”