I’m surprised there’s not more discussion as to why London - the most densely populated part of the UK - now has the lowest levels of infection.

More cautious behaviour? Fewer care homes? Some degree of herd immunity (even though likely <20% have had it). Genuinely curious.

Grateful for the many responses to this with a range of explanations. I'll attempt to summarise but there was a very good piece by @hannahdev in yesterday's Guardian running through the arguments. /2 https://www.theguardian.com/world/2020/may/15/regional-differences-in-covid-19-transmission-rate-emerge-in-england

A few comments along the lines of 'London was first in, so now first out' or 'London is further along the curve'. This may be true but doesn't answer the question why London is coming out now, especially if only a small minority have been infected. /3

Some have suggested that lack of testing or variable access to testing explains why London looks different. But, even accepting that there's lots we don't know & can't be very precise on the R number, scientific consensus is that London is different from the rest of UK. /4

The trends for positive tests, hospital admissions and deaths all show that London has moved from being a hotspot to a coldspot.

Is it that behaviour have changed more in London? Some evidence to support that from @jburnmurdoch. /5 https://twitter.com/jburnmurdoch/status/1261637732008370178?s=20

But then again, as @AdamJKucharski points out, Google mobility data looks similar for all cities. Also, he makes interesting point that perhaps community transmission across UK might be quite consistent, but the issue could be focused in eg care homes. https://twitter.com/AdamJKucharski/status/1261603310316007427?s=20

How much is the to do with the nature of London's population? London has a younger population but more densely populated & large BAME population. Does that explain why London making faster progress than elsewhere? How important fewer care home residents? /7

What about herd immunity? The implication of the 'London's further along the curve' argument is that there's more immunity in the community and it's harder for the virus to spread. But @AdamJKucharski makes the case against. /8 https://twitter.com/AdamJKucharski/status/1261602675021492227?s=20

Is it possible that we need fewer infected people than we thought to reduce significantly the level of transmission (because some people have much more contact with lots of people than others)?
Or have more people had it than we think? Antibody tests may tell us that soon. /9

Or is there immunity from other coronaviruses which means there's more immunity than we thought?
But it has to be said there's lots of scepticism from many scientists about any herd immunity explanation. /10 https://twitter.com/BallouxFrancois/status/1261636998936354816?s=20

I certainly don't know the answer to the question 'why does London now have the lowest levels of infection?' But it seems to me that the answer to that question (behaviour? demographics? immunity levels? etc) will tell us quite a lot. /END