[OutsiderFan]

Sorry, BC and Goose, but you are not going to convince me that these models are useful without data showing that they accurately predict the peak (in both timing and intensity), and we are way too early in this process for that.  The Gaussian curves they are using imply a specific relationship between the early "exponential" stages of the outbreak and the later leveling off and decrease.  There is no reason to expect that the Gaussian fits better than any of a number of other potential curves.

Imagine that someone knows nothing about gravity and wants to predict the arc of a projectile.  If they only have data from the first few seconds of the trajectory, when the motion is nearly linear, you could fit a tremendous variety of different curves to that data.  Even if you knew that the projectile will eventually return to earth, most of those curves would be totally wrong.  But you wouldn't be able to evaluate the curves until the projectile reaches its apex or nearly so.

That's where we are with covid-19.  It will eventually reach a peak and then decline, but the specific timing and height of the peak are unknown.  Fitting a curve to the first n data points does not necessarily tell you anything about the peak.  I am not a fan of those Imperial College models, but at least they are trying to model the mechanisms that generate the data, and that gives them a basis for projecting forward.  Fitting the curve that fits the first two weeks of data best does not tell you what is coming in the future.*

*I could change my mind with a convincing demonstration that arbitrary curve fitting for the first 2 weeks of past outbreaks was sufficient to model the course of an epidemic.  I doubt this has been done though.

Rachel Maddow interviewed the guy leading the UW team putting together the IHME projections. My takeaway is they are updating the models with new data constantly, and that they are building into them some optimism that states will take the proper steps to increase distancing. Every day states don't act as the UW researchers see fit, their best case projections become less optimistic. So for example, on Monday 3/30, the U.S. total expected deaths was pegged at 80,000. By Tuesday 3/31, after seeing so many states had not acted to their recommendations, the new estimate was 93,000 deaths.  Each day these states don't act the case, hospitalization, and death projections go up for them, adding to the U.S. projections.

The UW guy made clear that the low end of projections are based on an assumption all states have stay at home orders. Given only 30 do at this time, they feel there is a lot of upside to the projections. The White House/Fauci projection of 100k-240k deaths was probably a "special order" number they got for "give us the projections for if all states are shut down on Wednesday out to a week from Wednesday."  

The Governors of these states are literally killing their residents by not acting. We decided to start two kinetic wars because 3,000 people died on 9/11, but these Governors' lack failure to act for just one day are projected to kill 7,000 people, and nobody bats an eye. The U.S. death numbers are rapidly rising, and every day the projections are starting to look less like projections and more like reality.

As for the projection accuracy, we know Seattle area scientists have as solid an understanding of anyone in the country about how to project the spread of SARS-CoV-2 and also what steps it takes to mitigate and reduce it, because they now have access to a lot of data in Washington in general, but King and Snohomish counties in particular, that inform the outcomes based on what actions are taken, and more importantly, when.

[OutsiderFan]

Sorry, BC and Goose, but you are not going to convince me that these models are useful without data showing that they accurately predict the peak (in both timing and intensity), and we are way too early in this process for that.  The Gaussian curves they are using imply a specific relationship between the early "exponential" stages of the outbreak and the later leveling off and decrease.  There is no reason to expect that the Gaussian fits better than any of a number of other potential curves.

Imagine that someone knows nothing about gravity and wants to predict the arc of a projectile.  If they only have data from the first few seconds of the trajectory, when the motion is nearly linear, you could fit a tremendous variety of different curves to that data.  Even if you knew that the projectile will eventually return to earth, most of those curves would be totally wrong.  But you wouldn't be able to evaluate the curves until the projectile reaches its apex or nearly so.

That's where we are with covid-19.  It will eventually reach a peak and then decline, but the specific timing and height of the peak are unknown.  Fitting a curve to the first n data points does not necessarily tell you anything about the peak.  I am not a fan of those Imperial College models, but at least they are trying to model the mechanisms that generate the data, and that gives them a basis for projecting forward.  Fitting the curve that fits the first two weeks of data best does not tell you what is coming in the future.*

*I could change my mind with a convincing demonstration that arbitrary curve fitting for the first 2 weeks of past outbreaks was sufficient to model the course of an epidemic.  I doubt this has been done though.

Rachel Maddow interviewed the guy leading the UW team putting together the IHME projections. My takeaway is they are updating the models with new data constantly, and that they are building into them some optimism that states will take the proper steps to increase distancing. Every day states don't act as the UW researchers see fit, their best case projections become less optimistic. So for example, on Monday 3/30, the U.S. total expected deaths was pegged at 80,000. By Tuesday 3/31, after seeing so many states had not acted to their recommendations, the new estimate was 93,000 deaths.  Each day these states don't act the case, hospitalization, and death projections go up for them, adding to the U.S. projections.

The UW guy made clear that the low end of projections are based on an assumption all states have stay at home orders. Given only 30 do at this time, they feel there is a lot of upside to the projections. The White House/Fauci projection of 100k-240k deaths was probably a "special order" number they got for "give us the projections for if all states are shut down on Wednesday out to a week from Wednesday."  

The Governors of these states are literally killing their residents by not acting. We decided to start two kinetic wars because 3,000 people died on 9/11, but these Governors' lack failure to act for just one day are projected to kill 7,000 people, and nobody bats an eye. The U.S. death numbers are rapidly rising, and every day the projections are starting to look less like projections and more like reality.

As for the projection accuracy, we know Seattle area scientists have as solid an understanding of anyone in the country about how to project the spread of SARS-CoV-2 and also what steps it takes to mitigate and reduce it, because they now have access to a lot of data in Washington in general, but King and Snohomish counties in particular, that inform the outcomes based on what actions are taken, and more importantly, when.