If Australia is running a marathon in how it tackles coronavirus, New Zealand has opted for something closer to a sprint.

Last month, New Zealand ditched plans to mitigate or suppress the spread of COVID-19 and instead committed to totally eliminate the transmission of the disease within its borders.

Three weeks into its strict lockdown, its 'go hard, go early' approach appears to be working: COVID-19 cases have steadily declined despite an increase in testing, and the country may start to roll back its restrictions as early as late April.

While Australia is also seeing a steady decline in the number of new cases, Deputy Chief Medical Officer Paul Kelly said: "This is not a sprint. This is a marathon."

On Tuesday, Dr Kelly said Australia was "in a much better place than [he] thought we would be at this point", but warned social distancing measures were likely to be in place in Australia until September, at least in some form.

"There may be some opportunity to roll back some of the restrictions, but at the moment, we have to stay at course and the six months is an indicative time which will get us through winter, through the usual flu season, and then maybe a time to reassess."

New Zealand is now "the envy of the world", according to the Grattan Institute, which said the country had a "realistic chance" of eliminating COVID-19 within the next couple of months.

But in Australia, with a population five times the size, is elimination a feasible goal? And if so, at what social and economic cost?

A large upfront sacrifice

Up until mid-March, New Zealand was taking a similar approach to Australia in trying to flatten the curve, said Michael Baker, professor of public health at the University of Otago.

That included increased border restrictions, isolating COVID-19 cases, contact tracing and quarantine.

"Like most countries, we were pursuing the standard pandemic model … and that's written for influenza," Professor Baker, who sits on the National Technical Committee advising the New Zealand Government on its COVID-19 response, told the Health Report.

After reading the report on the WHO Mission to China, Professor Baker said it became clear the new coronavirus was more like SARS than influenza, and that eliminating the virus — even after community transmission had been established — was possible.

While New Zealand had a little extra "breathing space" — its first case didn't arrive until late February — health officials knew the country didn't have the necessary infrastructure to contain an epidemic.

"We didn't have large numbers of staff to do contact tracing, our borders were still a bit porous, and we were relying on a fairly soft form of self-isolation — home quarantine," he said.

Professor Baker and his colleagues encouraged the Government to radically escalate social distancing and travel restriction measures.

"A lot of things had to happen very quickly, and it became fairly obvious that we needed a complete, rapid shutdown of the country, just to give us time to get these systems operating, and also to extinguish some of the chains of virus transmission."

Stay home for a month

On March 23, New Zealand committed to an elimination strategy — one of the only Western countries to do so — and by March 26, the country entered Stage 4 restrictions: a full national lockdown.

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New Zealanders were instructed to stay home for a month, unless exercising outdoors (in which case they are required to stick to their neighbourhood), and to only interact with people in their household.

All schools and non-essential businesses have been closed, and only essential travel permitted.

Unlike a mitigation or suppression — where the response is increased as the pandemic progresses — disease elimination uses intensive early interventions to stop the disease spreading.

"As soon as you get any evidence of local transmission, you throw everything at it … and that's really what New Zealand has done," Professor Baker said.

"There is one model that's been done … and it says that after four weeks of lockdown, we might just be at [zero community transmission]."

While New Zealand is on track to meet its elimination goal, Professor Baker said the widespread lockdown had come at significant social and economic cost.

He said there was still "huge public support", but that the next challenge was deciding when and how to begin lifting restrictions.

"We have to be very confident in border quarantine, the ability to rapidly identify cases and stamp them out, and also thinking about the back-stop surveillance systems that have to be operating — so lots of testing," he said.

Australia already heading in the right direction

When asked whether Australia, like New Zealand, should set its sights on trying to eliminate COVID-19, Chief Medical Officer Brendan Murphy said it was one of the "potential strategic options to consider".

"The challenge with elimination is that nobody yet knows whether it's possible," he told RN Breakfast.

"You have to keep the most aggressive border measures in place for a very long time, potentially until you've got a vaccine."

Although not under total national lockdown, Australians have been required to stay at home and practise social distancing since mid-March.

Dr Murphy said it would be weeks before authorities could judge how successful Australia had been in slowing the spread of the virus, but that we were heading in the right direction — and there were few signs we needed tougher measures in the interim.

"Our track record over the past few weeks is looking pretty good."

In a briefing with New Zealand politicians on Tuesday, Professor Murphy said the aim of New Zealand's elimination strategy was not all that different from Australia's suppression and control approach.

"Our goals are very much the same; to get transmission down to as low as possible," he said.

"And if we get rid of it, that would be great."

Australia would "love" to eliminate the virus entirely, Professor Murphy said, but likened it to a "nirvana" that could not necessarily be achieved.

But he said both Australia and New Zealand were in a strong position because they had gone "hard and fast" in their response to the virus.

The pathway out of a pandemic

Jodie McVernon, who led the modelling used by the Federal Government to determine Australia's COVID-19 response, also said elimination was not an entirely realistic goal.

"I think the measures for elimination locally would be incredibly intensive and difficult to achieve, given just how infectious this pathogen is," Professor McVernon, of the Doherty Institute, told the Health Report.

"We know this virus is all around the world, we've seen how quickly it can be imported.

"It will become endemic, it will not be eliminated globally, and we will have to face it again."

Professor McVernon said it would take a vaccine to "definitively turn off the risk of infection", and that even if we got infection rates down to very low levels in coming months, we couldn't assume Australia would stay protected from a re-emergence of the virus.

"That's really where the challenge comes over the longer term — of how we deal with this in a sustainable way," she said.

Infected disease experts are expected to work with the Australian Government in coming weeks to find a path out of the coronavirus crisis as modelling focused on community transmission rates becomes clearer.

Prime Minister Scott Morrison said additional data would "help us plan the way out".

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But Kamalini Lokuge, from the School of Public Health at the Australian National University, said Australia should look beyond modelling and to our close neighbours to prepare an exit plan.

"We need to be looking at how we eliminate this disease from Australia, and then how we stay in elimination once we start lifting the measures we have put in place," Dr Lokuge told the Health Report.

"We've got real-world, very relevant experience ... that shows us that we can move towards elimination and we can get there quite quickly.

"The way we do that is to expand our testing capacity, to do very effective, farer contact tracing … and make sure our public health systems are ready and prepared to control any early transmission of COVID-19 in the community."

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Not clear when restrictions will ease

Despite the COVID-19 curve flattening, Prime Minister Scott Morrison said Australians must be patient and "we can't get ahead of ourselves".

"If you take your eyes off this thing, he gets away from you," he told Channel Seven on Tuesday, citing the examples of Sweden and Singapore.

"We are hopeful that at some point, we can move from the phase we are currently in to a new phase, but I do want to caution Australians that we're not in that phase yet."

Health Minister Greg Hunt said Australia would have to pass three tests before restrictions ended: a sustained decrease in cases, rapid response capabilities (in case individual cases broke out in a local spike), and a clear exit plan to gradually reopen businesses.

The danger of lifting restrictions too soon is that even a small number of infected people can result in a rapid, potentially disastrous rise in cases, Professor McVernon said.

"The distancing measures that are in place at the moment appear to be doing a very effective job of suppressing the rate of growth — but that's because they're in place," she said.

"If we ease up on the virus, it still is what it is is ... a highly contagious virus."