Data and analysis thread, started 12 November

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Data and Analysis Thread, started Oct 29 www.mumsnet.com/Talk/coronavirus/4064113-Data-and-Analysis-Thread-started-Oct-29

Regular lurker but I frequent poster, didn't want to lose the threads.

I think the issue with the instant tests is that they don't detect as many people as the lab processed tests do who had Covid a week or two back but are now recovered and no longer contagious. So they may only detect 60% of cases that would have been detected by lab tests, but this isn't 60% of the most contagious people, it's more or less all of them. That's the theory (based on the science behind how they work). We don't have clear evidence one way or the other because we can't actually measure test results against whether people are actually contagious right now. We can only compare one test against another. Could be they're giving false negatives, or could be the lab tests giving "false" positives (not really false, as the person has had Covid, but falsely suggesting they're currently infectious as they're actually not)

I've just noticed the dashboard, on the front page, now says "R number is estimated at 1 to 1.2" - which i'm sure is a decrease over the start of the week.

Specimen date wise, it looks like 9th may end up on a par or slightly higher than the 2nd, but very unlikely now to top it by much.

@PatriciaHolm I’d concur re Monday 9th.

Confirmed cases last weekend 17862 and 16541 at the moment are significantly up for weekend numbers.

Previous weekend 13345 and 14338

Then prior to that
13161 and 13521
11845 and 12349
9645 and 10148

I can see Tuesday just gone passing the case number for Tuesday 3rd.

All above numbers relate to England, I’d hope once we get into next weeks specimen dates a downward trend might start if the current lockdown is having an impact. So next wednesday’s reported number will be interesting as that will be the first indicator as to whether the Monday peak is starting to fall.

This chart from RP131 is quite good at showing how cases "build up". 9th looks to be at a similar level to the 2nd, 10th on track to be higher though possibly.

Ah ok fireflies, that's interesting, thank you.

Little statistic for everyone, on 29th March the UK reached 10,000 covid tests per day. 1st May was 100,000 tests. Progress is slow, but there is progress.

@Firefliess - one thing I've been wondering. With these lower sensitivity tests for mass testing, if they turn out to be successful at identifying enough cases to reduce R... would there would be consideration given to dialling down the number of PCR cycles - reducing unnecessary positives for people who may have had covid but aren't infectious?

My thoughts are that perhaps people should get one of 3 results; positive, negative and "low positive". The latter, I don't know how it should be handled, could be isolate e.g. 3 days, if you get more symptoms then you're on the hook for the whole isolation, otherwise free to roam. It would surely reduce some of the false negative fuss if people actually had proper explanation about what it means.

www.bbc.co.uk/news/health-54937486

I can’t see the report behind the news story, but children are now bringing more cases into households than adults for the first time according to this.

@MRex
That sounds a good idea, but I'm not sure whether you could distinguish a low positive from the beginning of the illness and the end. Possibly in conjunction with antibodies?

From the article:

"People living with secondary-school-age children were 8% more likely to catch the virus.

But research by the London School of Hygiene and Tropical Medicine and the University of Oxford found that people living with under-18s had no increased risk of becoming seriously ill from Covid."

The phrasing is so misleading. Hate it when they do that. Imo if you have +8% chance of getting it, than you have +8% of being seriously ill. Not because kids have bigger viral loads, but simply because they are 8% more likely to bring it home. Simple. Or I'm missing something? wouldn't be the first time.

Btw, I was saying a few threads back that Richmond and Kingston are not fining ppl. It's on their website.
Got a call from LEA who say: oh sorry, we must have forgot it from March. ffs.
And they ordered my boy in.

If it's an employer you have forums to go to and prove how it's not covid safe. Kids have no voice and no forums to complain to. It's unfair. Obviously our kid's attitude is driven in a big part by us, but at 15 he also has his own point of view. And he doesn't want to go in f2f either.

What's the current case mortality rate in the UK? I quoted the Johns Hopkins figure of 4% and an antivaxer told me it was really just 1% because of increased testing or something.

I can’t see the report behind the news story, but children are now bringing more cases into households than adults for the first time according to this.

BBC must've come up with its story after reading multiple SAGE documents that have been released earlier today.

The suggestion that older children may be introducing infections into their households was based on one of the weekly ONS infection pilot reports from mid-October. We discussed this data a while back. The evidence is not entirely conclusive (given limited sample and time series) - but it should definitely be reviewed further.

The most recent update to SAGE appeared more balanced than earlier (October) documents and included interesting case studies (Appendix B):

assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/935125/tfc-covid-19-children-transmission-s0860-041120.pdf

@TheSunIsStillShining You're completely right about the 8% thing. It's lazy journalism again failing to distinguish "there is no link" (between having secondary aged children and getting seriously ill from Covid) with "we have failed to prove a statistically significant link with the data we have available" If a truly matched group of people without secondary aged children were 8% less likely to catch Covid then obviously they'd also be 8% less likely to get seriously ill. Children don't have some magic protective power over their parents that ensures they only get Covid mildly FFS!

It's possible that any age matched group they tried to compare to without children had a disproportionate number of people with serious health problems (who are less likely to have children) thus cancelling out any observed impact of catching Covid from children. Or simply that the numbers they looked at were too small to prove a statistical significance (most parents of secondary aged children will be under 60 so not very high risk) But not remotely plausible that catching Covid does not put you at greater risk of getting seriously ill from it, compared to not catching it!

@Firefliess
I don't know how many phds, mscs, bas and other titles we have in between our ranks, but let's be fair, most of us are not rocket scientists* and we clearly see correlations, have hypotheses and can put scaffolding against our arguments. Bottom line is that we a just bunch of people who are willing to think and look for and at research. Evaluate and discuss the subject at hand in length besides running our everyday lives.

Would it be too much to ask the same from the people who are responsible for running this country??

*I apologise if someone actually is. I didn't mean it that way :)

Oh and thanks for the reassurance. :)

@GetAMoveOnTroodon

Interesting numbers from Liverpool today, in 7 days 430 people across the city tested positive, 200 with symptoms, 230 without.

That seems like quite a low proportion of asymptomatic people, especially as at least some of them will presumably go on to develop symptoms later. I had heard estimates of up to 80% quoted before the pilot started. Any guesses as to whether that's mostly down to genuinely lower asymptomatic case numbers than expected, or other factors such as asymptomatic people being less likely to get tested and/or to get a positive test result?

I would suggest that people who think it's unlikely they have covid would be less likely to be getting tested.

I was talking to dh and asked if we had mass testing round here whether he'd have it done.
He replied that there was no point as he hardly goes anywhere so would be very unlikely to get it.
Also my df was offered the antibody test. Again, didn't take it up because they'd isolated since beginning of March so couldn't have had it.

It would be interesting to know how many people who went for a test had any minorly unwell symptom that they "just wondered" if it might be one of the less common covid symptoms.

I had a maths tutor, who when teaching differential equations used to love to say “This is simple work, not exactly rocket science - except it is!” He used to always give us examples of rocket launches, and we would need to take into consideration the dwindling weight of the fuel and its knock on effect on fuel consumption. He was right, it wasn’t terribly difficult. Brain surgery, on the other hand...

see latest stats from Liverpool here. I think there’s a combination of factors.

1. people wfh aren’t bothering to get tested, so the asymptomatic tests are predominantly being done by those out and about still.

2. a significant chunk of those people are actually those living outside the city, Sefton’s numbers have gone up for the first time in a while on littleowls email I saw this morning.

3. they wanted to test everyone twice, so are now pushing for people to come back, be interesting to see if people do

The positivity rate is lower than you might expect from the asymptomatic testing in Liverpool, especially given what people are pointing out that those who work outside the home or have mild symptoms (headache, sore throat etc) being more likely to get a test.

One possible reason might be the type of test they're using. The lab processed tests pick up a number of people as positive who've had Covid weeks ago, many of whom will be asymptomatic at the time of the year. These new instant ones work a different way and are intended to identify those with current, active infections. So you'd expect fewer asymptomatic people to have sufficient levels of infection to show up as positive.

Another possible explanation is that Covid has been so much in the news in Liverpool that many people have been getting NHS tests when they have any symptoms at all, or possibly even if they don't, but have had close contact with a case. Unlike the asymptomatic people who are picked up in the ONS survey many of whom may have no idea they're at risk.

@TheSunIsStillShining - I'm not a rocket scientist (but I have worked with ex rocket scientists and they have each been very clever).
If a truly matched group of people without secondary aged children were 8% less likely to catch Covid then obviously they'd also be 8% less likely to get seriously ill.

Yes, very obvious. I think they've struggled with "truly matched" and given up somewhere, it is hard:

1. if you increase household size due to having children then you increase risk anyway compared with a single person / couple who may even WFH,
2. if you have secondary age then you may also have even higher risk 18-24 at home,
3. if your children are an adult (even if at home), then you're generally older and more susceptible to severe illness
4. flatmates may spend less time closely together than family (may not use shared meal pots, do each other's laundry, sit eating or watching TV together, give a hug/kiss goodnight etc).

We also have the old problem that some people simply can not take the risk of being told they can’t work.

MRex and TheSun, I really enjoyed getting my brain around your disagreement re school stuff in the last thread, even if you both felt a little exasperated at times! Was there any resolution? I have looked back at the last thread but can’t see it. As is so often with data debates there was logic on both sides so I would love to see how they might be reconciled. Please ignore it responding would drive you nuts, but accept congratulations for an impersonal debate.

Using data from the surveillance report, it's tricky to balance increases in cases against changes in positivity. Because when positivity goes down, even if cases stay the same that means infections are reducing.

With the increase in testing, positivity rates have all had slight drops this week except NE pillar 2 (12.8 to 14.2 %) and London stable on 10.4 %, which given the increase in testing means a true rise in cases. NW pillar 2 however dropped from 15.1 to 13.0 %.
However, Liverpool is on 4.8% positivity now, down from 13.6% the week before, 18.9% on 21st October, 24.8% on 8th October: liverpool.gov.uk/covidcases#:~:text=The%20latest%20weekly%20rate%20of,testing%20rate*%20is%204.8%25.
Yes, there's more testing and a worryingly high number of cases, BUT it looks like a city with the real infection levels steadily dropping to me.
Caveat - I haven't spent long researching, so if you think I might have missed something obvious, I probably have.

@Yummyoldbag and @herecomesthsun - glad to hear it was interesting. Exchange of thoughtful analysis is great, I don't remember where we left the point about 23rd August infections among secondary, because that is the only number in the way of a consistent rise since summer. I was challenged on comment about socialising outside school, and should confess I didn't repond with data because I thought the research on social contacts was too lightweight to use - so I was surprised to see Sage used it in their analysis and I guess it's all we have.
The coming weeks of lockdown, plus any local authorities who choose to swab schools regularly, should give more evidence on whether schools are driving infections. (But I suspect the picture will remain unclear and I also suspect the real answer is an annoyingly hazy "a bit"; because it drives some increases, especially with older school age groups, but isn't a major driver).