Test & trace app criteria..

[doireallyneedaname]

Does anyone know how the algorithm works? A friend that owns an establishment that had a Covid case was told that “15 minutes face to face contact” is the danger zone and I have also been told by others that is the scenario that will push the app to ask you to isolate - seems ridiculous as you can absolutely get infected with much less contact.

As far as I understand it the Covid app will trace up to a 100m radius, so if you (like me) last night had a notification re a recent “contact” having tested positive but advising there’s no need for me to isolate; theoretically it could have been someone 10 meters away whilst on one of my walks? I don’t actually go inside anywhere and certainly haven’t had any face to face contact in months!

From the .gov site:

We are interested in in the 48 hours before you developed symptoms and the time since you developed symptoms.

Close contact means:

• having face-to-face contact with someone less than 1 metre away (this will include times where you have worn a face covering or a face mask)
• spending more than 15 minutes within 2 metres of someone
• travelling in a car or other small vehicle with someone (even on a short journey) or close to them on a plane

Thanks! I did have a look but didn’t see that.

Don’t you find that concerning?

Not really, no

www.gov.uk/guidance/nhs-test-and-trace-how-it-works - from here

Did your app flash up with a disappearing notification? Thats been in the news and is a glitch and doesn't mean you have to isolate

I've been told twice now I've been in contact with a positive case but no further action was necessary.

I assume it was someone in either the supermarket or schoolyard as I don't go anywhere else and the only people I have prolonged contact with are my little bubble at uni once a fortnight and the uni would contact me directly if it was one of them.

www.mumsnet.com/Talk/am_i_being_unreasonable/4051544-covid-app-notifications

If it about the disappearing notifications then this thread has useful info

For me I got a notification saying the app was checking a positive contact then couple of hours later got one saying no further action necessary.

The disappearing notification glitch was fixed 08/10 (supposedly) - so any notifications should be legitimate.

It did follow up the original notification with a 2nd one telling me I don’t need to isolate

Yeah, that's the phantom notifications talked about in this news article
www.google.com/amp/s/www.bbc.co.uk/news/amp/technology-54522438

The phantom notifications will still come but you get a follow up message saying no need to isolate. If there is no info in the app itself then you are ok to ignore them

From the BBC article

Yes I've had these too. Schools are using the same approach to determine whether to send teachers home based on kids' cases. I know of two families where a DC has tested +ve but no one else in the family has, so it's not a done deal being in close contact with someone at any rate.

It just seems a bit risky to me. Obviously I’m not an expert but it doesn’t really take an expert to see that you don’t need face to face contact with someone less than a meter away to get infected

If it was that easy to catch then everyone would have it. You need a sufficiently large infective dose to get it so the longer you are with someone and the closer you are to them the more you will be exposed to it. The risk is smaller the further away you are and if you are only close to each other for a short amount of tine

@doireallyneedaname

It just seems a bit risky to me. Obviously I’m not an expert but it doesn’t really take an expert to see that you don’t need face to face contact with someone less than a meter away to get infected

You can, but it’s far less likely than in the scenarios for close contact that they use. They’ve had to make the determination on where to draw the line to catch the most potential cases, without shutting everything/one down continually.

Measles is much more contagious with an R0 of 12-18 whereas covid 19 seems to be have an R0 of somewhere around 3 if measures aren't taken to reduce it.

Passing someone quickly is unlikely to pass on anything unless they speak or cough directly into your face at close proximity