Thinking through how ICU admissions are affected by community case numbers, I looked at the COVID19 figures for Victoria, Aus (from https://www.covid19data.com.au/  ).

With apologies for my data viz skills, the lag from rise in cases >> hospitalisation >> ICU admission is clear here.

The regional lockdown in Victoria seems thankfully to have been effective in decreasing new cases, and so, hopefully, the ICU admissions should follow that decrease with a lag, but obviously things are a bit different this time around than in April

There's probably a few things to think through from looking at second waves from around the globe and how the figures differ from March/April . One thing is around proportions of the severely ill and speculation as to why that might look different https://www.ft.com/content/c011e214-fb95-4a64-b23c-2bd87ebb29d7?shareType=nongift

Aside from a possible lag to hospitalisation, ICU admissions and deaths (which may mean they still go up) the other most obvious thing that means apples are not being compared to apples, would be testing rates.

It's likely that the actual infection rate in places like the UK and the rest of Europe was way higher back then, just not picked up, so the proportion progressing to severe illness may have seemed higher . https://twitter.com/AdamJKucharski/status/1298902546271133696?s=20

Another explainer might be that different demographics are being infected now, particularly around age but also co-morbidities. This is particularly pertinent, in the other direction to the UK, now in NZ, where a far more vulnerable population may be affected this time and next.

Strain on healthcare systems may also be lower in various places and in-hospital mortality is almost certainly related to healthcare strain.
Additionally systems of care and knowledge will have improved.

All these explanations seem more plausible than the population immunity one, yet that is the one that gets more airtime in some quarters.
It seems unlikely the disease is less severe now and there are many groups who would be hit hard if it took hold in NZ.

So I think the best take home from looking at global disease patterns would be that the pandemic is not homogenous. The same numbers do not necessarily paint the same picture.

Here’s a brilliant, well written explainer by @DrJinRussell on exactly that

https://twitter.com/drjinrussell/status/1299162471307948036?s=21 https://twitter.com/drjinrussell/status/1299162471307948036

As an additional note @DrJinRussell is well worth following on this platform if you are looking for smart, scientific and well written explainers on the pandemic, particularly as it pertains to NZ.