[stupac2]

 The decline would happen more quickly because of fevers from pathogens with shorter incubation times, which is basically every common illness, right? Yes, good point!

 But I'm not sure you can safely pick out a few dozen cases of covid out of what must be tens of thousands of background fevers.
I assume they are applying appropriate sophisticated statistical techniques to determine what is a significant signal. Their consultants and peer-reviewed publication evidence this sophistication in the past. They have not yet published this study with its methodology.

I'm sure it's sophisticated, but this is just a really hard problem. You have a small (but probably increasing) signal riding on a large baseline and now that baseline is changing rapidly because of an intervention that's trying to affect the signal. I'm not sure how you predict what's supposed to happen there, it's a unique situation so the previous years' data won't be too helpful.

[stupac2]

 The decline would happen more quickly because of fevers from pathogens with shorter incubation times, which is basically every common illness, right? Yes, good point!

 But I'm not sure you can safely pick out a few dozen cases of covid out of what must be tens of thousands of background fevers.
I assume they are applying appropriate sophisticated statistical techniques to determine what is a significant signal. Their consultants and peer-reviewed publication evidence this sophistication in the past. They have not yet published this study with its methodology.

I'm sure it's sophisticated, but this is just a really hard problem. You have a small (but probably increasing) signal riding on a large baseline and now that baseline is changing rapidly because of an intervention that's trying to affect the signal. I'm not sure how you predict what's supposed to happen there, it's a unique situation so the previous years' data won't be too helpful.