He and the premiers may indeed have navigated to the point that some of the controls can be loosened soon. But they know well the dangers of prematurely declaring victory, and the reasons for extreme caution in doing anything that increases the risk of an upsurge of fresh cases - this time almost all of domestic origin rather than from recent travellers abroad.

Here and in the United States are commentators saying that the time to go is now - if it wasn't a fortnight ago. Some seem quite indifferent to the fact that this increases the risks of death, particularly among the infirm and the old, arguing, reasonably enough, that society always seeks to draw a balance between general public safety and economic health on the one hand, and risk of death and injury to individuals on another. Thus, for example, our speed limits can be described as an effort to weigh the convenience of speed with the risk to people who get in the way of cars and trucks.

We build bridges and high-rise buildings knowing that there is a substantial risk that workers may die in the process. As our concern about this rises, we may increase occupational health and safety rules and the disincentives for bad practice. But we can never entirely eliminate risk and the public would seem to agree that the benefit of what is constructed outweighs the human costs. Those arguing the sums will claim, of course, that the very existence of the bridge or building may save lives that should also be put in the balance, or create wealth that allows others to enjoy better health.

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These are political choices, for politicians to make. We hope, of course, that they take expert advice about the relevant risks. In the case of COVID-19, we hope, of course, that politicians attach a great importance to human life and are repulsed by those whose agitation for an immediate resumption of business as usual is indifferent about some casualties. A time comes, nonetheless, when it can be argued that the general damage to the economy, and the human misery that causes (including, perhaps suicide) outweighs the real risks to the lives or the health of a few.

It's a judgment politicians have to make, one which cannot be avoided unless government is so prepared to use coercion to enforce its will that the general need for a consensus about social costs can be ignored. But not everyone will agree what that point is, and critics will make politics about anything that can be argued to be a misjudgement, or a callous misjudgement. Look for example at Tony Abbott's entirely unjustified but highly successful campaign blaming Keven Rudd personally for the deaths of some roof insulation installers, on the basis, apparently, that it ought to have been obvious to Rudd (though not to installers) that stupid people might put nails in live electrical wire. The Abbott campaign and its consequences was much aided by a partisan section of the media. But it was also much helped by the fact that the Rudd government failed either to explain and sell its program, or to defend itself against attack. Likewise Scott Morrison will be blamed for any deaths if he returns the economy to normal too early.

Morrison has already discovered that when an epidemic is loose in the community, those who call for stronger measures against the disease will always seem more virtuous and public spirited than those who hesitate to impose controls they know will be unpopular. If Morrison ever had any hopes that his "national cabinet" would operate under some sort of doctrine of collective responsibility - bound for example by a vote - he was quickly disabused. Premiers and chief ministers were keen to co-operate, but they would always put their own circumstances and needs, as they saw them, ahead of consensus when it seemed to them to matter. Thus the two most populous states - one Labor and one Liberal, who were already stretched by COVID-19 cases - read the situation differently from the outlying states, where there were fewer cases. This led to different decisions about school closures, and about strict quarantine controls at the borders. Morrison had to be nimble to obtain a general consensus open to local variations, and to be philosophical about it, even when he was furious.

The combined effect has exceeded all hopes and expectations, and raises the prospect that whole regions of Australia will soon be free of active COVID-19 cases, or acute ones requiring major hospital intervention. The theory is that the virus is infectious for no more than a fortnight, even among those who are asymptomatic or have it so mildly that they do not associate it with coronavirus. Getting to this point has been assisted by forced isolation of travellers and efforts to limit human movement. If, after a fortnight with such controls, there are no fresh cases, one can regard that region as free of the virus.

That's a situation which will continue only as long as no person arrives from outside the region carrying the virus. She may have no symptoms, and no consciousness that she has been in contact with another carrier. We now know from actual research, as well as general principle, that asymptomatic and mild cases shed and spread the virus as much as florid cases, and that some of those infected will go on to develop serious, perhaps fatal COVID-19. One can use screening devices on roads, public transport, docks and ports, but it is almost inevitable that some cases will get through. With a high proportion of the population having no immunity (at least until there are vaccines) just one person can spur a fresh epidemic calling for the reimposition of controls.

At least until the vaccine, the virus, like the poor, will always be with us. Its impact on the population will differ. Most young children, other than those with existing autoimmune diseases, asthma and on cancer treatment, may completely avoid any sort of severe complications if they get infected, although their secretions will be a risk to those with whom they come into contact. Most adults up until 50 will not develop severe symptoms, unless they already have conditions - perhaps diabetes, autoimmune diseases, respiratory conditions or they smoke, in which case their susceptibility may be similar to those 20 years older. From 50 on, a significant proportion of those infected develop severe respiratory (sometimes gastric) complications. Severity and fatality seem to increase markedly with age. Apart from the already frail, or those who have predisposing conditions, frontline medical workers are at considerable continuing risk - and not necessarily by getting it from someone currently infected, but by picking up a virus 10 or more generations older than any about at the moment.

It seems, right now, unthinkable that Australians would abandon the interests of those who are already sick, older parents, and grandparents. One must assume that there will be continuing efforts to keep the "hump" as flat as possible, and that all will get care, at least until a point where available care must be rationed. That said, it is almost inevitable that the general public will tire of continuous containment measures - controls on travel and association, bans on free movement, social distancing, and loss of income from work. These restrictions may be lifted in a staged way, with the public told that some will be reimposed if there is a fresh upsurge. But it is not hard to guess that it will be difficult to get effective compliance with restored tight controls when there is a resurgence. That will be the time when Australians decide that a certain mortality and level of long-term disability is acceptable.

Americans have so epically mismanaged the coronavirus that it is difficult to look to it for lessons. The same might be said of most of the nations of western Europe, including Britain. But the blame lies more on their politicians than on their scientists. Underfunded, at times castrated, and with dissidents punished as badly as if they were blowing the whistle on China - America still has a critical mass of knowledge and resources that overwhelms anyone else.

The New England Journal of Medicine predicted in an editorial late this week that the political requirement to crank up the American economy again was going to prove, in its body politic, almost irresistible, probably by the end of June. If America wanted to limit fatalities while doing this, it must not seek to flatten the curve but to "crush" it. "China did this in Wuhan', it said. "We can do it across this country in 10 weeks."

It specified six requirements. Four were familiar to us here:

There are two other recommendations worth studying, here as well as in the US. Both require more real-time fundamental research. First (actually sixth in its list):

Good luck to the United States with that. At both national and state levels, leaders were slow to act, and the population is paying the price, with infection rates (per 100,000) many times those in Australia and New Zealand, (or China and most of South East Asia), and death rates at even higher proportionate levels. With President Donald Trump so eager to declare victory and depart the battlefield, the prognosis must continue to be grim, including in areas close to some of his base constituencies so far only lightly dusted by the virus. If Australia was suffering at the rate of New York City (about a third of Australia's population), we would have had about 450,000 cases and 34,000 deaths. Some tiny mass surveys suggest that one in every seven people has or has had the virus. By comparison, Australia has about 6700 confirmed cases (76 per cent of whom have recovered) and 75 deaths. The New York death rate is about 450 times the Australian one. This underlines the success we have had.

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California has a population 60 per cent bigger than Australia's. It has had more than 35,000 confirmed cases, and more than 1350 deaths. Australia has fewer than 7000 cases, and 76 deaths. We must be doing something right, or them something very wrong.

California is a Democrat state with a greater attachment to coronavirus reality than many of the Red states of the union. It has had fairly drastic efforts to isolate and quarantine, push social distancing and shut down the economy, and is being much more cautious about opening up for business again.

At this stage, the Governor, Gavin Newsom, is refusing to set any sort of artificial deadline and says it depends on progress with six key indicators - improving its capacity to monitor and track cases; prevent infection of high-risk people; increase surge capacity of hospitals; develop therapeutics and ensure physical distance at schools, businesses and childcare centres. And to have an agreed set of guidelines about when to ask Californians to stay home again if the virus surges.

Newsom says he might be able to predict some sort of end date in about a fortnight, if new cases begin to go down. He's also strongly into expanding testing beyond sick patients to find out how many of the general population is infected, and how many have immunity.

COVID-19 figures from the US, Europe (including Britain) and mainland China are so much greater, proportionately, than our nation that it is difficult to use them as a guide. I should think, however, that mass testing would suggest that more than 100,000 Australians already have an antibody response to the virus, but will not be caught up in the screen we have so far because they have had few symptoms (and have now recovered). They will have mostly infected people who likewise showed no symptoms. Perhaps 5000 to 10,000 (most unknown to the authorities) are currently infectious, if not in a way that is bringing many cases to doctors and hospitals.

My point - I have repeated it in a number of columns - is that continually increasing numbers of tests on people thought to have or to have been exposed to the virus is not a substitute for mass testing, and the results of such tests (now down to about 2 per cent positive) are not a guide to maximum incidence or prevalence. Australia is still doing all too little genuine random mass testing, and, as a result, we know too little about the real size of our problem, or about the chances of a resurgence. If it has had a sort of justification - the need to ration testing equipment - that no longer prevails.