Pogue Mahone
Closet Gooner.
On Delta and its transmission ability compared to the original Wuhan strain:
We know from previous studies that people are at their most infectious on/around the day they get symptoms. With Delta it looks like they're actually more infectious due to the higher vital load.
Combine that with a faster infection to infectious timeline (down from around 6 days to 4 or less) and it's easy to see how Delta got a transmission advantage.
What it means in terms of spread is the thing the epidemiologists are now musing over. More super-spreaders and super-spreader events? Which might explain the speed of the jump in cases in Scotland, and maybe even the fact they soon started to fall again. Probably the end of test and trace (using human tracers to do phone contacts) as well (assuming it still exists at all).
I wonder if the shorter timeline might paradoxically be a good thing? More explosive increase in cases but shorter overall duration of each surge. Arguably the worst thing about this virus is the very lengthy disease course, which means we get horribly lengthy incidence spikes. If it operated on the same timeline as, say, influenza the whole pandemic would probably be done and dusted by now.