What rapid virus spike really means

The news today that Victoria has recorded another 75 new cases of coronavirus in the past 24 hours, continuing a trend of sharp daily increases, has added to talk of a “second wave”.

Could it be the first warning sign that Australia’s overall success in flattening the curve is about to come to a devastating end?

Victoria was just beginning to emerge from its strict lockdown measures when the flare-up began, forcing a reintroduction of bans.

The declaration by New South Wales Premier Gladys Berejiklian that Victorians shouldn’t cross the border, and that her citizens should avoid travel south, highlights the seriousness of the resurgence.

Authorities say the situation is likely to get much worse, given the benefits of renewed restrictions and a rapid testing blitz across 10 suburbs won’t be felt for weeks.

Professor James McCaw from the Centre for Epidemiology and Biostatistics at The University of Melbourne initially wondered whether the uptick was just a blip that could be managed.

“The pendulum is starting to swing towards this being more than a statistical blip,” Prof McCaw said.

“While there is no apparent uptick in hospitalisation yet, it is too early to tell why. It may be that cases are in younger people picked up by the targeted testing system who are less likely to become severely ill.

“Or it may be that in a few weeks time we will see increasing hospitalisations as the infection spreads further.”

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The term “second wave” has almost become part of the Australian lexicon this year … but what does it actually mean?

Professor Marylouise McLaws is an epidemiologist and infectious disease expert at UNSW and said a second wave of infection follows an extended period of zero new cases.

“Normally, that’s twice an incubation period,” Prof McLaws said. “In this case, 28 days.”

After that, a second wave would look like “a sudden return of the same sort of infection rate, or worse, than was seen the first time around”.

But Victoria never got to a sustained period of new recorded infections.

Curiously, there’s no agreed scientific definition of what specifically constitutes the second wave of an infectious disease, but experts say they know it when they see it.

“You’ll see a rise involving a second group of people after infections in a first group have diminished,” epidemiologist Dr Jessica Justman from Columbia University’s Mailman School of Public Health said.

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This makes it tricky when talking about the COVID-19 situation in countries like the United States, which never really experienced a significant decline in case numbers.

In that sense, America is still experiencing its first wave – albeit a very large one.

“Do you want to call it an extension of the first wave or a second wave superimposed on the first? You could argue it either way,” Dr Justman said.

Dr Eric Toner, a senior researcher at John Hopkins University, doesn’t find talk of “waves” overly helpful.

“When you’re underwater, it’s hard to tell how many waves are passing over your head,” Dr Toner said. “The virus isn’t going away and coming back. The virus is still here. It’s up in some places and down in others.”


Health officials in South Korea last week declared the country was in the midst of a second wave, after a sharp spike in new infections in the capital Seoul.

That’s after the country was celebrated as an infection control model for the rest of the world to follow.

Jeong Un-kyeong, director of the Korea Centers for Disease Control, said the surge can be pinpointed to a holiday weekend in early May.

“In the metropolitan area, we believe that the first wave was from March to April as well as February to March,” Mr Jeong said. “Then we see that the second wave which was triggered by the May holiday has been going on.”

Crowds of young people flocking to night clubs over that holiday period, as well as well-attended indoor church services, are believed to have amplified infections.

In February, daily case numbers peaked at 909 but by April they’d fallen down to single digits.

However, the numbers have picked up again, with new case numbers spiking at the end of May to 79 in a single day. Since then, the average daily new cases have hovered between 30 and 58.

“As long as people have close contact with others, we believe that infections will continue,” Mr Jeong said.

As of Monday, South Korea has a total of 12,757 cases – 42 new infections in the past day – and a death toll of 282.

In Iran, the number of coronavirus infections has passed 220,000 and at least 10,000 people have died since the first reported case in mid-February.

The Middle Eastern nation hit a low in new daily cases in early May, but rates are on an upward trajectory once more.

As a result, authorities have mandated the wearing of face masks and reintroduced lockdowns and bans on mass public gatherings.

Israel has also declared it’s experiencing a second wave, after recording an uptick in new cases.


Prof McLaws describes the unfolding scenario in Victoria as “a perfect storm” of factors.

“It’s a community transmission mainly pushed by three large family clusters, it’s the interconnectivity of those cluster groups, and it’s the infection of health providers and staff in quarantine hotels,” she said.

But it doesn’t represent a second wave, she believes.

“It’s a spike, a resurgence of significance and a worrying trend, but I wouldn’t call it a second wave.”

Not only is it not a second wave, but it’s a sign of more to come – not just in Victoria, but potentially elsewhere, Professor Raina MacIntyre, Head of Biosecurity Research Program at the Kirby Institute, said.

“This is the new normal until the day we have an effective vaccine and can vaccinate everyone,” Prof MacIntyre said.

“The pandemic is getting worse globally. We will be living with the virus and intermittent epidemics for some time – we need to make sure we can control the epidemics as they arise, anywhere in Australia.”

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While Victoria is the current focus of attention, the conditions for transmission are largely similar across the nation and outbreaks are a genuine possibility in all states and territories, Prof McCaw said.

“It is important to keep in mind that cases being reported today reflect transmission activity some one-to-two weeks ago.

“Likewise, responses put in place today – and changes in behaviour that may occur spontaneously as people realise that the virus is still here and continues to pose a major threat – will not be reflected in reported data for another one-to-two weeks.”

Jeremy Rossman, a senior lecturer in virology at the University of Kent in the United Kingdom, said the concept of “waves” implies the pandemic is “a force of nature that’s beyond our control”.

But there’s strong evidence that the opposite is true – and it presents a strong lesson for Victoria, and indeed the rest of Australia, to take note of.

“A strong public health system, consisting of widespread testing, contact tracing, isolation and health support, combined with public participation in safe behaviour – wearing face coverings, keeping physical distance, hand washing – is highly effective at minimising COVID-19 transmission,” Mr Rossman said.

“We are in an ebb and flow of COVID-19 transmission that is continually affected by our precautionary actions. Letting up on precautions will lead to an increase in cases.

“This is the new normal and what to expect until we have an effective vaccine with significant population uptake. Until then we have to depend on our actions to keep cases low.”

– With wires

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