Six months....impossible

Originally posted by madamswer: ↑

Baffling stats (and many conflicting ones) abound when it comes to this virus.

It was always known that what would ultimately transpire would only be observable ex-post facto

Especially in relation to the two most determining variables, namely:

1. The actual infection rate, and
2. The mortality rate.

And not just in raw aggregate terms, but in terms of distribution across demographic groupings.

The first variable, how infectious this virus is, will remain indeterminate (since we don't know what we didn't know in terms of what the number of undiagnosed cases was at each point of the testing timeline). But I have to say, for a country with a lockdown that started quite late in the piece and which is clearly far from comprehensive [*], that Australia has only had some 6,500 reported cases of this thing (with a maximum number of cases at any one time of less than 5,000 cases) doesn't make too much sense to me.

But the second variable, namely the mortality rate, can be measured with increasing accuracy as the data set becomes larger and more representative over time.

Of the 3,555 closed cases, we have had 61 deaths.
So that equates to a maximum mortality rate of 1.69%.
(Maximum, because there would have been a number of recovery cases that were not reported.)

Now 1.69% as a mortality rate might sound high, but if one looked at the demographic distribution of those deaths, all but one of them occurred in the sub- 60 year old cohort.

So, if we work out the mortality rate of that sub-60 year old part of the population (which is 78% of the population, i.e., some 19m people) it is derived by dividing the number of deaths by the number of closed cases in that cohort.

I have not found a reliable source that breaks down the closed cases by age category (but the government does provide the number of reported cases per age group), so one approach is to use the proportion of reported cases per age group as a proxy for the proportion of closed cases in each age group.... recognising, of course, that the number of unreported per capita recoveries will be a lot higher in the younger ages than in the over-60s.

So using number of cases in age age group as a proxy for closed cases for each age group appears to be reasonable and, if anything, conservative approach.

According to the Department of Health, around 70% of the cases reported occurred in the sub-60 year old category.
So, applying that 70% fraction to the total number of closed cases, we get an estimate of 70% of 3,555 = ~2,500 of recoveries in the sub-60 age category.

So that works out to a mortality rate of 1 divided by 2,500, i.e., 0.04% in the sub-60 year age cohort.

(And again, that's the maximum mortality rate because it is based on only recorded recovery cases, and not recovery cases which are not observable.)

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In that context, it will seem increasingly incongruent to keep the entire country in wholesale lockdown, at the cost of hundreds of billions of dollars of economic contraction and the attendant loss of livelihoods and all the multitude of social ills that accompany that.

I strongly suspect that before long, a moderated lockdown strategy will need to be adopted - broadly along the lines of keeping the most vulnerable citizens (plus-70 year olds) in lockdown - but freeing the bulk of the population to continue with their jobs and livelihoods.

Using a sledgehammer to crack an egg might have been fine at the outset when we didn't know what we were dealing with, but now the real-time data provides some critical insights which suggests to this observer that the universal and indiscriminate lockdown approach has served its purpose and that a more targeted approach is going to be required before long.

[*] Heck, a little more than a month ago, we were boasting about fitting a record number of people into the MCC for a cricket match!

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I'm not sure if you intended to construct your post based on the domestic mortality rate, but it seems your view of what the future should or could look like is. There are a few concerns I have with framing the argument in that way, however I broadly agree that as we get more certainty around the scientific data we can design our response in a more measured way.

The main concern I have with your observations is you suggested that Australia's mortality rate is quite low, and extremely low for the under 60's. You quite rightly point out that our experience has been quite different from other countries, however I think you incorrectly land in a position which suggests that we are somehow different. I would suggest our experience is different because of a few possible factors.

1. Longer lead time for crisis and travel response
2. Lower density of population
3. Quicker acceptance of our society towards social distancing
4. Warmer climate
5. Younger population

There could be many more I've missed, but I think it's a common miscalculation to think Covid-19 "Isn't that bad" because it's currently not that bad. If we look at the experience the U.S and U.K is having, it's not hard to imagine how it could be a lot worse here, much the same as people quickly forget why vaccines are important. In the face of and escalating crisis I think your opinion might change a bit (which is what we are currently trying to plan and prevent for). We are all in real danger of exercising social will on governments while the curve flattens under the false security that all is well. There is a real risk that if we take our foot off the brake, things could get a lot worse, and it will be incredibly hard to restore confidence in the population again, at least until there is a vaccine that doesn't cause autism.

I accept the argument that we can have more targeted policy response which can include quarantining the more at risk, as well as a staged essential opening of the economy, but lets not lose sight of how bad this could really be, just because we are in the "Lucky Country".