We've gone from near 60k cases a day to just under 25k cases per day in about 10 days, is something fishy going on?
Drop is real I think, the positivity rate is dropping also from July 21st which is in line which what should happen with infection numbers beginning to drop from the same time.
I think we're bouncing along around the herd immunity threshold. That threshold isn't an exact set figure for this virus, more a range where it comes into play depending on the values of certain things that govern transmission levels. Population behaviour, population immunity, weather/seasonality and the virus characteristics all play a role in governing those transmission levels. Virus characteristics are consistent (for now at least), weather has been good decreasing transmission, population immunity increases daily and also strengthens daily, so also decreasing transmission. The variable one at this moment really is population behaviour.
Putting July 21st to one side for now we can consider what actually went on for late June and all of July up to that point. We had increasing social contacts due to football culminating in a Euro final where social interaction was likely the highest it's been in 18 months. Just prior we had university terms ending and the associated increased social contacts that entailed. We recently also had schools shutting from 3 weeks ago which are now all on holidays. We've also had increasing numbers isolating as we went through the last 6-8 weeks.
Adding all those together in some sort of timeline we get A) increasing contacts from end of university term which peaked and then faded, 2) overlapped by a rise in contacts due to football which peaked at the final and subsided and 3) the end of which overlapped with schools shutting for holidays. You can almost look at those things as a kind of slow lockdown being enacted - daily contacts went from high to low, essentially what a lockdown aims to do. I think what we're seeing now is us approaching that range for herd immunity for the population circumstances as they are now (or were at July 21st).
Those circumstances will change with worse weather after the Summer and schools back, but on the flip side population immunity will hopefully continue to increase. If as it seems that we are bouncing around that range, the future looks like maybe being bumps rather than waves. I think there's a lot to be optimistic about at the moment. I also think we may have overshot the threshold that step 4 will bring, at least over the next few months with the social interactions that went on during the final 10 days of Euro 2020. So we may not see another significant rise in infections from step 4, rather it will just cause it to plateau at some level - maybe along with very small and transient rise when we get to that level as the delta variant fills out the remaining infection space step 4 leads to.
