Australia faces some hard truths when deciding how to combat the coronavirus pandemic that has the country locked down, according to experts.

Key points: Two medical experts have explained Australia's coronavirus strategy

Two medical experts have explained Australia's coronavirus strategy They say flattening the coronavirus infection curve here could take between six to 12 months

They say flattening the coronavirus infection curve here could take between six to 12 months In that time, one argues at least 60 per cent of the population would need to be infected

Australia's deputy chief medical officer Paul Kelly says combating the virus can be divided into two main schools of thought.

These are known as "flatten the curve", which Australia is using, and "eradication", a harsher lockdown which New Zealand is trying.

According to University of Melbourne epidemiologist Tony Blakely, there's something many Australians don't realise about the strategy being enacted here.

What 'flatten the curve' actually means

Professor Blakely says the strategy favoured by the Federal Government is not designed to stop transmission.

Rather, it aims to slow it to a manageable level so hospitals don't get overwhelmed.

"You don't go in too hard because you actually want the infection rate to pick up a bit and then hold," he said.

Shutting down non-essential services and encouraging people to stay home and isolate are strategies designed to slow the spread of COVID-19.

"What they're not saying is [that] 'flatten the curve' likely means [that] by the time this is over, 60 per cent of us will have been infected, to develop herd immunity," he said.

Professor Blakely argues this type of herd immunity is the only way to ensure there is no resurgence of the virus once physical distancing and shutdown restrictions are lifted, and borders are re-opened.

Herd immunity — when a large proportion of a population has immunity from a disease because they have either been vaccinated or previously contracted it — disrupts chains of infection, and helps protect everyone.

And that means a majority of Australians would need to contract coronavirus to keep the rest of the population safe.

Field epidemiologist at the University of Newcastle, Craig Dalton, says under the "flatten the curve" strategy the number of beds in intensive care units would serve as a guide as to how high the numbers of confirmed cases can be allowed to rise.

"When it comes to lifting restrictions it's like turning the tap of cases on or off depending on how full hospitals are," he said.

Sydney has been deserted since the coronavirus lockdown. ( ABC News: Glen Moret )

Epidemiologist Professor Hassan Vally, from La Trobe University, said herd immunity was not straightforward, and warned it would be "reckless" to deliberately spread the virus through the community.

"Letting the virus run through the population just doesn't make sense. We would be left with a lot of deaths and our health system would be overrun," he said.

"We know it's not just people over 80 who are susceptible to this virus. We already have young people in hospital and intensive care, too."

Some people in the United Kingdom initially pushed for a more rapid spread of the virus to help develop herd immunity, but Dr Vally said that thinking had since been abandoned.

"We want to slow the transmission of the virus and ultimately stop its spread [in Australia]," he said.



What's the other option?

The "eradication" strategy means trying to contain the virus completely, but Professor Blakely and Dr Dalton both believe it is a gamble.

This week, New Zealand's Government implemented a massive month-long COVID-19 crackdown.

Police are patrolling the streets, and everyone who is not an essential worker has been ordered to stay home.

No interactions with people outside the family home are allowed, and all schools are closed.

"It's not guaranteed to work — maybe a 50:50 shot," Professor Blakely said.

The strategy requires borders to stay closed or be strictly controlled until a vaccine arrives. That could be 12 to 18 months away.

Dr Dalton says while he prefers this strategy, it would require containing every case of the virus — or risking a resurgence once the lockdown was relaxed.

He says it is too late to do that in Australia.

"Four to six weeks alone will begin blunting the force of it, but I don't think it's enough, we'll need to be fairly restrictive for six to 12 months at least," he said.

Circular Quay is usually a popular spot for tourists. ( ABC News: Glen Moret )

When will we know which one works?

NSW Chief Health Officer Kerry Chant says it will take seven to 14 days to know if the "flatten the curve" measures are working.

The data is being closely watched so the success of the strategies could be measured.

The challenge for those in charge is finding the least-worst solution.

"One is go hard and go fast, the other is about a scalable proportionate response," Professor Kelly said in a press conference.

A difficult decision for our health authorities, in desperate times.