Yeah, that IHME model.. It's unfortunate that it's become the model most people have become acquainted with. It has its uses, but the down-slope has previously generated critiques.
Good Carl Bergstrom thread: https://twitter.com/CT_Bergstrom/status/1250304069119275009
A few select quotes from that thread:
> 6. But this is a mix of two different processes, an acceleration phase prior to control, and a deceleration phase once controls are in place. Given that, why does the model predict symmetric death curves?
> 7. The answer is that this is a modeling assumption that the research team has made. They have chosen to fit a particular sigmoidal curve called the Gaussian Error Function (erf function, for short) to the data representing the cumulative number of deaths that have occurred.
> 13. The actual trajectory tracks the forecast pretty closely, but then starts to turn around. Once that happens, the back side of the curve is constrained to mirror the front side; the epidemic is predicted to wane quickly. By May 17, the uncertainty range collapses to 0 deaths.
> 14. This strikes me as unrealistic. Even ignoring the real-world coupling between states (this is not included in the model), I am not persuaded that the epidemic will necessarily be entirely finished in just over a month.
And a very important point he brings up:
> 16. In defense of the model, every model is a tool with a purpose. The primary purpose of their model is to predict peak health care need, not the endpoint of the outbreak. That said, people need to be aware of a model's purpose and be cautious when using it for anything else.
In other words, it's actually a pretty bad model* for predicting the down-slope. I fully expect that we'll hit 100k deaths for this first wave.
*unless the US were to have done a Wuhan-style lockdown.