Sunday, March 29, 2020

COVID-19: the weeks ahead

The figures below (#deaths) are from the Financial Times (data updates frequently). It's useful to compare NY and US numbers to Lombardia and Italy. In the former case we can extrapolate the slope on the log plot for another week or so, because lockdowns here are recent and death generally happens +2-3wks after infection. For Lombardia / Italy we can start to see some bending of the curve from lockdowns that started about 20 days ago.

Based on these simple observations, I think NY will be ~10k in a week, US perhaps double that. Comparing with the Italian curves, US would be lucky not to reach ~100k by end of April -- i.e. 4 or 5 doublings in next 4 wks, or 2.5k x (16-32) = 40-80k.

In COVID-19 Notes (March 8) I gave my best estimates for key parameters characterizing the epidemic:
1. R0 ~ (2-3) or higher in a permissive environment -- no strong efforts at social distancing, quarantine, etc.

2. Fatality rate: roughly 1 percent of cases, heavily concentrated in older individuals and/or those with pre-existing conditions. Note this assumes a well-functioning health system and resources for the 5% or so of cases that need intensive care. See below.

3. In situations like #1 above, doubling time could be as short as a few days. Number of infections in Italy grew by ~1000x over the month of February -- i.e., 2^10 or 2+ doublings per week!

80 percent mild case
15 percent serious (may require hospitalization)
5 percent ICU
I think these numbers will turn out to be roughly correct. For the cognoscenti: German CFR numbers have been steadily increasing, just under 1% now, SK increasing to about 1.5%. Diamond Princess deaths have reached 10, perhaps more to come.

This is from a widely-circulated post by a New Orleans ER doc:
I am an ER MD in New Orleans. Class of 98 [Texas A&M]. Every one of my colleagues have now seen several hundred Covid 19 patients and this is what I think I know.

Clinical course is predictable.
2-11 days after exposure (day 5 on average) flu like symptoms start. Common are fever, headache, dry cough, myalgias(back pain), nausea without vomiting, abdominal discomfort with some diarrhea, loss of smell, anorexia, fatigue.

Day 5 of symptoms- increased SOB, and bilateral viral pneumonia from direct viral damage to lung parenchyma.

Day 10- Cytokine storm leading to acute ARDS and multiorgan failure. You can literally watch it happen in a matter of hours.

[ NOTE: (2-11) + 10 = 2-3 wks after infection ]

81% mild symptoms, 14% severe symptoms requiring hospitalization, 5% critical.

... Our main teaching hospital repurposed space to open 50 new Covid 19 ICU beds this past Sunday so these numbers are with significant decompression. Today those 50 beds are full. They are opening 30 more by Friday. But even with the "lockdown", our AI models are expecting a 200-400% increase in covid 19 patients by 4/4/2020.

... Everyone is scared; patients and employees. But we are the leaders of that emergency room. Be nice to your nurses and staff. Show by example how to tackle this crisis head on. Good luck to us all.
Judging from the video below, I would guess that there are at least ~1 million people in NYC among whom the infection rate has been rapid (~3 day doubling timescale) for a long time, with little to no reduction due to the lockdown. If this is correct, we can expect a huge number of deaths and critical cases from this population alone -- perhaps 10k deaths, 50k critical cases.

Added: This is an interview with one of the leading CV-19 experts in Korea. Not much new for readers of this blog, but a good introduction for the general population. Perhaps most interesting: discussion of masks at @15m (droplet and aerosol transmission just before that), followed by the Korean approach to the epidemic. Alarmingly, @8m he describes known cases of individual re-infection after recovery!

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