My back-of-the-envelope COVID model
A friend used the metaphor that COVID new cases to hospitalizations and deaths was like a swell hitting the buoys at sea accurately predicting the size of waves we would see at our shores in the days that follow. Curious, I decided to run a very simple back of the envelope modeling.
I used the following simple assumptions based on CDC ranges for the US.
- 7 days from COVID exposure to symptoms and a test positive
- 14 days from symptoms to an immune response causing hospitalization
- 14 days from hospitalization to death
Using those simple assumptions, I did a quick model for today, December 12th
- We have 110K US hospitalizations who were exposed 2–4 weeks ago (11/14–11/28)
- We had 2.5K deaths who were exposed 5 weeks ago (11/7)
- There were ~2.1M new cases 11/14–11/28 driving today’s hospitalizations (based on ~150K/day)
- 2.1M new cases to 110K hospitalizations is a ~5.2% hospitalization rate
- 110K new cases on 11/7 led to 2.5K deaths which is a ~2.3% death rate
Using today’s numbers here’s a swag of what we might expect on Christmas Day
- Hospitalizations will be based on exposures 11/28 to today, 12/12
- With a 5.2% hospitalization rate on those 2.8M cases (~200K/day), we will have 146K hospitalizations on Xmas assuming there is bed availability.
- With a 2.3% death rate on the 150K new cases on 11/21, there will be 3.4K deaths on Christmas assuming everyone that sick gets the same hospitalization care available today.
The model is flawed and simplified for the sake of being easy to follow. Today’s hospitalizations and deaths are obviously based on November's new cases. Hospitalizations and deaths on Christmas can be predicted based on behavior through today, 12/12. Future numbers may be higher or lower than this simple model predicts but the point is the same.
There’s a reason every doctor, nurse, and scientist is terrified about the impact COVID will have on this country in the months to come. Like the Titanic which filled too many hulls to stay afloat, at the rate of 225K new COVID cases per day, it’s a mathematical certainty we will run out of beds which will increase the death rate because people can’t get the care they need to survive. As the percentage of people sick in our community, your risk of becoming sick increases if you are out and about.
I’m lucky. I got COVID in February before we knew what we know now and while I was a long-hauler with months of fatigue and breathing issues caused by lung damage impacting my ability to exercise at previous levels and leaving me with a permanent case of asthma, I’m fine. There are many others like me, healthy with no pre-existing condition or risk factors, that aren’t so lucky.
Please be safe and careful in the weeks to come my friends and family!