Is that assuming that around half of those that test positive (with the current testing/sampling methodology) die?
My initial thought was "no, not at all. I'm simply assuming the current 10-day lagged ratio of new cases to deaths remains constant."
But I went back and checked my model, and it's showing a horrifying death rate for new cases of 54%.
Sense-checking this, there were 6,700 total confirmed cases on 22nd March, and we've had 2,900 deaths in total, which would be a 43% death rate even if you assume that no deaths at all have occured from confirmed cases since 22nd March.
(It seems that reported "new cases" are actually hospitalised cases, and the above death rate refers to infected people who are in the 2nd stage of the virus, where it becomes much more serious and hospitalisation is required.)
Reuters are reporting a Govt source says the UK government has a worst case death toll of 50,000 if social distancing was only 50% adhered to, but they are saying a "good" outcome would be under 20,000. (Obviously "good" is a relative term for a disaster like this.) Source also expects Easter Sunday (April 12th) to be peak day for deaths.
My assumption of a 10-day lag is based on taking a weekly average of new cases % increase (16th-22nd March) and weekly average of death % increase (26th March-1st April). These figures are 24% and 26.5% respectively, showing a reasonable fit. To estimate deaths in future days, I've plugged in %new cases increase from 10 days earlier.
Adding in 20% from care homes, it seems inevitable that 17,000 deaths will occur based on existing 2nd stage infection cases. Assuming the latest reported %increase in new cases (14.6%) is replicated tomorrow would give 20,000 deaths by Easter Sunday.
To make that the peak day for deaths, I've assumed the %increase in new cases goes down tomorrow to 10%, then 8% the next day, 6% the day after, then 4%, 2% which would give 27,000 deaths by 17th April.
This assumes the social distancing measures start to really kick in from tomorrow (in affecting new cases) and show a dramatic improvement.
It's reasonable to assume social distancing measures should kick in any day now giving an immediate reduction in % increase of new cases.
I've been optimistic in my assumption of how quickly and how sharply social distancing will affect infection growth rates, but more pessimistic assumptions don't change the total deaths by more than about 7,000.
The key driver in the number of deaths is the exponential growth rate. Compared to the actual lockdown date, a lockdown 3 days earlier would have halved the deaths, lockdown 3 days later would have doubled deaths.
I've also assumed the NHS doesn't get overwhelmed by the new cases, and death rate remains unchanged. If this isn't the case, there could be in the region of 5,000 extra deaths.
However, we need to remember this is just the initial stage of the virus. After this first wave, the virus will still be present, and loosening of the social distancing measures will see further waves of new infections and deaths.
I'm afraid this is a very bleak picture, but I'm simply trying to make sense of the numbers, and give some estimate of what may happen, in a dispassionate way.
Social distancing needs to start working very soon, be very effective and also to be very sustained if we are to have any hope of keeping the death total below 50,000 in this first phase.
Today's 2pm figures will be absolutely crucial - we desperately need to see the % increase in new cases reduce from yesterday's 14.6% to below 10% either today or tomorrow.
Please note, there is absolutely no praise/criticism of the government, NHS or public behaviour in my post, and I wouldn't want this thread to descend into any sort of political point-scoring (there's also Polite Discussions for that).
I'd be very interested to see anyone's alternative methodologies and thoughts on this.