UKH

Whilst waiting for the weekly release of the PHE Surveillance Report (which is getting later and later each week...) I noticed they've added reports for hotspots at the LTLA level:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/... 1

These are I think really interesting and relevant to the discussions on other recent threads about why the fatality rate is so low using recently reported data, and if this is to do with (a) the virus becoming less lethal vs (b) better isolation of the more elderly from infection.  What makes them so useful is their presentation of a demographic and time breakdown in testing results, limited to  areas with enough cases now to give some meaning to the data.

Here's my interpretation - what's yours?

• In the March/April period, there was a similar ratio of Pillar 1 cases (detected in hospital admissions) between 18-64 year olds and 65+ year olds across most of the regions, which accounting for demographics means hospital admissions with Covid were well biassed towards the 65+ age range - where the fatality rate increases dramatically.
• In the the July/August period, the detected cases are perhaps 8x larger in the 18-64 age range than 65+ compared to the earlier period; this shows to me unequivocally that we are doing a ~ 8x better job of isolating people over 64 years of age from exposure to infection.  Cases are now largely confined to Pillar 2 (cases detected in the community)...
• It’s worth noting that if the Pillar 2 data had been taken in March/April to now, that it would have been perhaps 80x higher than the Pillar 1 data at the time.  
  • Without accounting for the massive scale up in targeted community testing, it appears that the virus is causing a smaller proportion of the infected to be hospitalised, but really we've ramped upsetting massively so this is highly misleading
  • It may be that still a smaller fraction are being hospitalised; with almost nobody seriously ill, almost nobody is likely to be shedding a very high viral load that perhaps causes others to become more seriously ill...  I haven't seen case observation data that's particularly compelling either way.  Thankfully the number of people being hospitalised is so small that there's not much significance in the data.

Agree with your bullet 1.

Agree about the data on bullet 2 although I think the terminology that we are "doing better" is perhaps slightly misleading. I think it's primarily a function of (1) 65+s are being far more cautious, (2) hospitals were pin the first wave the main transmission risk for a long time and contain high numbers of 65+s generally, but they now have a much better idea how to avoid unnecessary transmission than they did in March, (3) we are testing most* people with symptoms rather than only people who go to hospital. I don't think there is an improvement of this type particularly because of any conscious decision that has been made or improved policy.

Not sure about your bullet 3.

The other thing I took from the data is that if you look at the shape of the people-tested curves, the areas that have seen outbreaks have generally had a much more marked uptick in the tests undertaken in the last 1-2 months (especially Leicester, but also other areas. This is positive because it shows people are taking advantage of the extra testing availability. It does also have the implication probably of further increasing the number of minor cases that get picked and hence further reducing the skew in the test data towards serious cases.

*Based on recent personal experience and subsequent reading I have done, I no longer have confidence that testing people with a fever, persistent cough or anosmia will pick up as high a proportion of cases as we would like. It's extremely difficult to determine when a cough is"persistent" and in many cases whether someone gets a test will depend how much of a problem a positive result would be for them. There is also some evidence around that a significant proportion (order of 20-25% I think) of infected people get primarily gastrointestinal symptoms and would not be picked up as covid potentials under the current system.

It’s true that “diagnosing” people to determine whether to test or not (and give self-isolation advice) is far from clear cut. People present with a whole range of symptoms and determining whether a cough is persistent isn’t straightforward, kids get short spikes of high temperature, positive cases can have none of the defined symptoms. Kids in particular can have GI symptoms. In reality deciding whether to test or not depends a bit on the risk that person presents  (based on occupation/vulnerability) and the current testing capacity. 

BBC reporting that test may be too sensitive and is picking up ‘dead’ virus following an infection. 
 

However that would still indicate lower fatality levels. All it changes is whether to lock down on areas where the cases are ‘apparently’ growing, but may be historic.