Melbourne coronavirus case numbers may spike, but experts say that's less cause for concern than you might think - ABC News

As Victorians adjust to a return to life under lockdown conditions, locally acquired COVID-19 case numbers of four and five over the past few days have served as a source of hope.

The total number of cases linked to this outbreak, 35, is not ideal, but it's also not like those daily figures in the hundreds the state grappled with last year.

As the number of exposure sites surpasses 150 and contact tracers continue tracking down 15,000 contacts of positive cases, including 3,000 primary close contacts, there are signs those low single-digit case numbers we have taken solace in may not be here to stay.

But as experts have explained, as long as the new cases we see remain linked, an increase in locally acquired cases will not necessarily be cause for serious concern.

Is it possible cases have already peaked?

Brigid Lynch, the president of the Australasian Epidemiological Association, said, considering the number of exposure sites and close primary contacts that had been identified, having only a handful of new cases was "actually really reassuring".

But she said it was likely they would increase in the days ahead.

"There is certainly scope for cases to rise," Dr Lynch said.

"But the number of cases isn't really the thing that's most concerning.

"Even if there were 30 cases tomorrow, if those people were all already identified and isolating at home, then that's not as worrying as finding a couple of cases that are out and about in the community."

Australasian Epidemiological Association president Brigid Lynch says as long as new cases are linked, they are not too much of a worry.(

Supplied: Brigid Lynch

)

She said it was very feasible that there would be a higher number of cases in the days to come.

"The risk is that not everyone carefully reads the website and checks the exposure sites," she said.

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Greg Dore, an infectious diseases physician and epidemiologist at the Kirby Institute, said cases would not necessarily increase over the next few days.

He said the outbreak might have already reached its peak.

Professor Dore said even if there were still three or four new cases popping up by next Tuesday or Wednesday, it would not mean the circuit-breaker lockdown should be extended.

"That wouldn't worry me at all," he said.

"As long [as there are] two things. One, those cases are linked to other cases; and secondly, those cases are detected among people who are already in quarantine."

Is this variant particularly infectious?

The jury is still out because there are gaps in knowledge about the subtype of the variant that has been identified in the Victorian outbreak, B.1.617.1.

Greg Dore, infectious diseases physician and epidemiologist at the Kirby Institute.(

Supplied: Greg Dore

)

The COVID-19 variant was first detected in India in October last year and has since spread to dozens of countries around the world.

There are signs that the subtype identified in Melbourne is more infectious than previous versions of the virus, but there is still more work to be done.

Professor Dore said there was evidence that the closely linked subtype, B.1.617.2, which has been circulating in the UK, was more infectious than other variants.

"This particular variant in Melbourne is closely related, as the numbering suggests, but we've got less information about this strain," he said.

"There's no solid evidence yet that it's more infectious."

He said when strains were more infectious, the reason appeared to be because they had higher levels of the virus.

"Some of these new strains do appear to have a higher overall viral level," he said.

Here's what you need to know about Victoria's COVID outbreak:

Does this variant have a shorter incubation period?

Well, according to Professor Dore, not necessarily.

He said there are other factors at play affecting perceptions of the strain's incubation period.

Professor Dore said incubation referred to the time between someone being exposed to the virus and developing symptoms.

He said during an outbreak, when contract tracers were finding people who had been exposed to COVID-19, asking them to isolate and testing them, it could make the incubation period appear shorter than it is.

"You clearly can be positive for the virus one or two or three days prior to developing symptoms," he said.

"So because you're swabbing everyone, you're detecting the virus before they're actually developing symptoms."

An almost empty Southern Cross Station on Saturday as Victorians took heed of restrictions introduced as part of a circuit-breaker lockdown.(

ABC News: Darcy Hodgson

)

According to Professor Dore, the intense contact tracing going on in Victoria at the moment means that the incubation period is being, in a sense, shortened "artificially".

He said another contributing factor was that early in an outbreak, the people experiencing shorter incubation periods were being picked up first.

"If you had 100 people running a marathon and you took the first 10 people who finished the marathon and you averaged how quickly they ran the marathon, it would be a much shorter period than if you waited for everyone else to get to the finish line," he said.

How realistic is a quick return to no community transmission?

While the state remains in the grips of the lockdown, it's difficult to consider what might happen too far in advance.

As Health Minister Martin Foley reiterated yesterday, the situation must be approached "day-by-day".

But both Professor Dore and Dr Lynch were very optimistic about Victoria's prospects of returning to no community transmission quite soon.

"It's definitely achievable — what we're seeing now is nothing like what we were seeing in 2020," Dr Lynch said.

"The figures of vaccination we have seen over the past few days suggest that everyone realises vaccinations are critical and important."

"The first vaccine you can get, you should take, because that's the only way we will get back to some normality."

What you need to know about coronavirus:

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2021-05-29 14:01:16Z
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