SARS-2 March 24 Update

First, the update:

03-24 Tuesday
1-day Projection: WW 425953/18600; PRC 81595/3283; NON 346031/15382; IT 69104/6744; US 57310/731; TX 916/10
Actual Numbers: WW 417966/18615; PRC 81591/3281; NON 336375/15334; IT 69176/6820; US 53740/706; TX 955/12

03-25 Wednesday
1-day Projection: WW 461807/21005; PRC 81686/3288; NON 381238/17782; IT 74856/7654; US 66137/903; TX 1203/16

Infection spread appears to be reducing in US and TX, even though TX was above projections for yesterday.
US shows 134% instead of 135%, and the last 3 days were 130%, 131%, and 123%.
TX shows 135% instead of 147%, and the last 3 days were 108%, 121%, and 126%.

This implies that the declaration of pandemic may have had positive effect.

The numbers from tonight or tomorrow will start reflecting any changes caused by the declaration of national emergency.

Milestones would have pushed out a day, but my methodology was poor. I now show the number for the condition in the left of the note, not the estimated number for that day. Also, I dropped stage 2 here, and just show worst case reserve (smallest number) and best case reserve (largest number). I do not have proper numbers to separate stage 1 (over standard) vs stage 2 (over minimum reserve).

04-10 146k TEXAS ICU STG3
04-11 178k TEXAS VENT STG3 & Hosp STG1
04-14 400k may be the inflection point for Texas
04-15 532k TEXAS HOSP STG3

Milestones are based on guesstimates, because the exact number of ICU beds and placement of ventillators is proprietary data that is hard to find and confirm. My estimates are based on: TX 28.7m pop; 2.9 beds per 1000 in TX (83230); 32% unoccupied (26633) / 11% are ICU (2929); 6.7% ventilators (1787); 10% limited function ventilation (2663) / 5-15% conf need hosp(532k-177k @ overrun); 2-10% ICU (29k-146k); 1-5% need vent (36k-178k)

Testing infrastructure may fail before the inflection point, leading to a false decrease in numbers reported. If that happens, we may not numerically reach the inflection point, which is 60% of the population for R0 of 2.2. Remember, we only confirm 12-15% of the actual cases, as many are mild or even asymptomatic, but are still infectious to others.

I expect these to move further out each of the next few days, and then it will probably look like it levels off a bit for several days before reducing further.

We are not out of the woods. Hospital usage is 1-4 weeks. Average infection course is 20 days with no hospitalization, but once people are bad enough to need O2 or ventilation, it takes longer to recover well enough to not need it anymore.  If we were to fall to 112% today (unrealistic extreme) and stay there, the milestone dates become 04-23, 04-25, 05-07, 05-09, 05-16, 05-18. That spreads out enough that we may gain an extra couple of days on each due to early cases resolving (people do not stay in the hospital forever).

The current milestones for the US, since TX is about 9% of the US:
03-31 29k -> 322k US ICU OVERRUN STAGE 1
03-31 36k -> 400k US VENT OVERRUN STAGE 1
04-05 146k -> 1622k US ICU STG3
04-06 178k -> 1977k US VENT STG3
04-08 400k -> 4444k US inflection point
04-09 532k -> 5800k US HOSP STG 2

These are MUCH more fuzzy, since it is not exactly 9%, and ICU, Vent and bed capacities vary. That adds 1-2 days uncertainty. This also will be affected by any changes in the numbers as discussed above.

Here are the milestones from 04-23 data for comparison to track our progress flattening the curve:
04-10 150k TEXAS VENT/ICU STG2 & Hosp STG 1
04-13 366k TEXAS VENT/ICU STG3 & Hosp STG 2
04-15 660k TEXAS Hosp STG 3

NOTE that the very first milestone was 04-02 based on 570 ICU beds, and was abandoned as a predictor.

When testing and behavior are nonchanging:
Model is +/- 25% per week
That is +/- 1.5 days for stage 1
That is +/- 2.5 days for stage 2
That is +/- 3.5 days for stage 3

Inflection point for R0 of 2.2 is 60%.
Current reporting rate is 12-15%.
Assuming we keep testing by same criteria, the Tx inflection point is 400k confirmed.
We may not reach this numerically due to testing/infrastructure failure.
eg, we may reach stage 3 while our confirmed rate is much lower, but still around the same days.

This is all bistromath, and both reporting rates, and trends are changing daily at this point.

Also note that the numbers lag by up to 24 hours based on reporting systems.

Also Also note that it still takes around 12 days for action changes to affect trends, since people infected today will not be detected for a while.

Also Also Also note that there are many people who have NO symptoms at all, but are still infecting others. This, along with poor testing, explains the 12-15% confirmation rate.

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