Loading Complete societal change. Good luck putting a six-month deadline on that. McCaw is a mathematical biologist. His colleague at the Doherty Institute and the University of Melbourne, Jodie McVernon, is a doctor and epidemiologist. Together they led the scientific work that underpinned the government modelling released this week. The public modelling was underwhelming because it was based on overseas data from weeks ago, but this highlights the way huge decisions had to be made in rapid succession with limited data in recent weeks. There are good questions about the work so far. Why is there no public modelling using local case numbers? When can we know whether closing a bar is more effective than shutting a school? The answers will take weeks.

The truth is the country’s top scientists are working under immense pressure to focus a microscope on a moving target. Their advice this week, in a teleconference held after Scott Morrison released the modelling, was to be wary of assumptions about what happens next. So the way out is yet to be found. Morrison rejects the strategy of herd immunity – the idea the country could be resistant after the infection reached perhaps 60 per cent of the population – and Health Minister Greg Hunt aims to keep infections well below 2.9 million people (the implied figure in the most benign published scenario). Loading But they also know that suppressing the virus for too long will drag out the economic damage. A point comes where too many restrictions will work against the country as a whole, and where calculations are made about the cost of saving lives. The medical experts are grappling with this challenge.

“There is a real risk the societal cure we choose may do more harm,” wrote Tony Blakely, a University of Melbourne professor of epidemiology (but not one of the Doherty Institute team) for The Conversation this week. “Lockdowns, for example, cause drops in GDP and increases in unemployment. That feeds back on to changes in suicide and heart disease. We need to quantify that, and weigh it up.” This will be the next phase in the debate. With more modelling about the shutdowns, rather than the virus alone, the argument will shift towards easing the constraints. Inside the Morrison government, one of the worries is that the economic damage could kill more people than the virus. Loading The solution is to relax the restrictions in stages and in different locations. Morrison may want this but cannot dictate the terms. The states and territories will make their own decisions because each has a different case load. It is tempting but misguided to debate a simple calculation – how many lives are worth sacrificing at the altar of the economy? – but the fact is that most of the cost cannot be avoided. The world economy is in shock. Australia cannot stop the slump.

Even so, nobody should be naive about the decisions political leaders and their governments must make in this crisis. They have rejected herd immunity but they have not promised eradication; their objective is to manage the deaths without overloading the hospitals. If the scientists are right, the recovery will not run as the politicians wish. While the Parliament’s new law stops the wage subsidies on the last Sunday in September, the virus is a law unto itself. Even if the government halts the JobKeeper payment of $1500 a fortnight, can it really halve the JobSeeker payment of $1100 a fortnight – that is, return to the old Newstart rate – six months from now? Loading Replay Replay video Play video Play video It seems unlikely. It would require Morrison to put jobless Australians back on the old subsistence rate when independent economist Saul Eslake forecasts the ranks of the unemployed will double to almost 1.4 million.

The recovery will not be swift enough to make that decision easy. Restaurants may reopen one day but the borders will remain closed. It will be Fortress Australia all this year and beyond. That is why “sovereignty” was Morrison’s key word in his speech to Parliament on Wednesday. Can Australia grow at all when it is locked off from the world? That may be the experiment until a vaccine arrives. Loading McVernon and McCaw are trying to prepare Australians for a lasting change. McCaw cites the Spanish influenza of a century ago as a warning. That epidemic arrived in three waves over nine months but did not stop there. “For the next five or six years there were elevated levels of disease activity from that same virus as it settled down and became a part of our ecosystem,” he says. “And then it was there for decades afterwards.”