Tuesday, May 26, 2020

Laissez-faire pandemic management - nudge fudge

The UK government has engaged in a series of psychological games with the population, instead of actually taking effective action.

Early on, an attempt to get people to socially distance was offset by the failure to enforce the shutdown of large gatherings at sporting events such as the Cheltenham Festival or football and rock music venues. Eventually, the footie community, as well as hotel chains and theatres, voluntarily closed before the government made it mandatory, presumably out of respect for their staff & customers. This may have cost them dear in some cases, as the insurance companies may decide that since it wasn't legally enforced, cancellation costs may not be covered in many cases. Similar attempts to assume it was someone else's problem - The NHS will get its own PPE and ventilators as if by magic; someone else will decide if people maybe should wear masks in public; perhaps the evidence on what constitutes early onset warning symptoms like loss of taste and smell aren't necessary to list just yet; sure, care homes will have their own safe procedures and equipment, just like hospitals, no? and sending people there from hospitals makes total sense.

Then there was the drift into an increasingly ill-specified lockdown, with many vectors for infection (e.g. London underground&busses, all international airports) completely open - i mean for heavens sakes, if the infection isn't spread by people packed into trains and planes like sardines, when not in their own homes or workplaces, how do they think it got from Wuhan to Wolverhampton? Or Downing Street to Durham?

On that last point, the latest nudge was clearly an underhand means to break lockdown early, without bothering with the unseemly debate between  people that actually care about the loss of life due to a second wave of infection, and the people who care about loss of revenue because of the economic slowdown that lockdown has imposed.

Ironically, the economic damage was mostly caused by the total failure to show any steel will power and take early action, which would have not only saved a lot of lives, but meant we could have been cleanly, honestly, and safely out of lockdown weeks ago.

The government have become the enemy of the people, both for our health and for our wealth. Given their alleged politics, that is quite an achievement.  I'm not a conspiracy theorist. I think it is because we have a system of finding elected representatives that selects for the utterly inadequate.

Thursday, May 14, 2020

Re-identifying your social network from contact trace&test decentralised apps

Obviously, some people are uncomfortable about the app that holds your contact data for the purposes of helping warn people they may have been infected, so have devised decentralised apps to achieve same goal. however, they kind of miss the obvious. 

There's no point in the app unless people act on notifications. acting entails i) isolating ii) getting tested so if negative, can stop isolating as soon as possible. if positive, can get treatment.

If you don't want to act on notifications, don't run the app.

So now what happens when a contactee is tested?

A simple re-identification of people is do-able 
if the case rate is low and largely localized.

So if patient A is first new person on day D tested +ve in city C, and then their set of decentralized possibly infected folks F are notified and  go and get tested, and say this shuts down the outbreak, then the testing agency knows that the set of F people are contacts of A. It doesn't get too much harder to do this probalistically if there's a slightly bigger outbreak with a few As and Fs in a city/locale, based on timing...

If the case is high and not localized, contact tracing and testing has failed, and we are in a second wave. and there are lots more dead people.

So centralised or decentralised, you have to trust the test center people. who (in the NHS case) are basically the same people.

Saturday, May 09, 2020

My home's too smart for me...

We had the builders in. It started when an old cooker broke - having fixed it twice, i though, lets just redo the kitchen. then we thought, why not extend it into the garden a bit so its lighter and so it began.

Firstly, an architect, and party wall agreements.

Then engineer survey says that the 10m eucalyptus tree in our garden means the extension needs 2m foundations.

Then we decide to move utilities to the basement (washing machine etc). then we need ne central heating setup so 1st  room gets new cupboard with that in. then the sitting room (which opens out to the garden or now, the new kitchen-garden room/extension) needs re-doing (new power points every where which is good) - basement also needs some air circulation gear.

So new kitchen/extension has a small new bathroom in the corner, which is cool, and nice tiled floor which is neat, but that has underfloor heating which needs smart controllers. and  the rooms all need new smoke alarm systems. builder puts in a "mesh" net of stufff that runs off nest and so forth...
i  couldn't figure out at all how to actually turn off the underfloor heating - just put it in "holiday" mode, which says its off unless it detects a frost..obviously the smooke alarms have motion sensors  so you can find your way around at night (or smoke)....

fridge is smart too, apparently (if we want, when we're away, if ever again, and deciding to come back early (or late) can remote set everything back from holiday mode...)...

Now water pressure in top of house is too low, so need pumps in the attic....which trigger off water pressure, so if you leave a tap running, you can tell from the racket in the attic...

So then while doing sitting room, decide hey why not open up the old (early 19th century- apparently late georgian according to the chimney sweep) fireplace there, and close the one in an upstairs (1st floor) bedroom. oh, and why not just redecorate the 1st floor loo, and get some nice Portuguese tiles. oh, and lets just refit the 3rd floor bathroom too while we're about it. and the terrace above the kitchen. needs new tiles and parapet to be legal too...

Did I mention that meant all the plumbing and most the electrics in the house had to be redone (re-routed and replaced).

It does look nice, though...

A bit more than my annual salary, it bloody should:-)

Tuesday, May 05, 2020

Arguments for NHSX centralised approach to contact tracing.

1/ The NHSX Bluetooth works - it doesn't require the phone to be always on.

(incorrect assumptions by DP-3T critics claiming it does) and isn't blocked by Apple/Google - it won't kill your battery any more than using a BLE peripheral (e.g. airpods:) it is a  bit of a hack. and may place limits on detecting  some contacts.

2/ The "contact" proxy is pretty much based on what we did in fluphone a decade back so also fairly solid indication of proximity, but may need adaptation (as will all BLE based contact tracing apps whether centralised or decentralised). updates to the parameters in the algorithm can be computed in centralised approach somewhat more easily than decentralised (where you don't have the false -ve/+ve rate info).

3/  The rationale for centralising the data is several fold, which are nigh on impossible with decentralised apps:

a) You can update the algorithm in 2 based on measuring false positive/negative rates (there are other factors in deciding a contact is real too) - you can incorporate factors about the contactees in computing risk of infection, given the measured parameters of  the encounter.
b) The narrative script people use for self-reporting can be updated based on ROC that that achieves
c) You can detect hotspots in infection near real time (e.g. superspreader events).
d) Epidemiologists potentially get to run models on pseudonymised social contact graph < this is where you might baulk but they aren't publishing the data - it will stay put, and models be updated from that - if hackers gain access to this data (how?), then there's a risk some people's graph could be partially re-identified. there's no geo-loc data in the phone or uploaded data so probably rather limited threat - if data is deleted (as claimed) in 30 days, then that threat is also time limited...
4/ There's a human-on-the-loop in the self-diagnosis phase (drawn from pool of people that deal with manual contact tracing) (and obviously also in actual test if that's triggering a notification) they can decide there's no problem, which can revoke the notification to contacts (rather hard to do in decentralised apps). This limits cascades from false positives.
5/ Contacts of contacts (etc) can also in principle be notified (useful in small, fast local outbreaks/clusters - a real problem in this virus) - again, difficult to do in decentralised model meaningfully
I'd welcome hearing how the decentralised app folks will tackle some of these useful
In common to all app based contact tracing is the acceleration over manual tracing, which has a marked impact on reducing the R0 of the pandemic. Contrary to claims that you need 60% of the population to be running the app, actually any number of people will help reduce contact times so reduce R0 - so it starts to be useful at low levels of deployment (as already pointed out, the epidemiologists find it useful at low levels already too since it lets them see SEIR parameters and spot any changes).
There's a lot of misinformation out there (nothing new about that:)

Ref white paper on NHSX app design.
Ref Limits on reduction of R0

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misery me, there is a floccipaucinihilipilification (*) of chronsynclastic infundibuli in these parts and I must therefore refer you to frank zappa instead, and go home