What's causing the UK Pingdemic?

Public health guru Linda Bauld talked to Chris about the 'pingdemic':

Linda - Well, it's interesting, isn't it? In fact, in a single week, over 500,000 people got a ping, a little message on that app and were advised to self-isolate. So these people are people who have been contacts of what we call the index case, which is the first positive case. So somebody tests positive, they have the virus, and then the app finds out who they'd been close to, normally around less than two meters for 15 minutes or more. There's other ways of identifying contacts, where you would ask the person who is the positive case, who have they been in contact with? The reason this is happening is just because as I was saying earlier, we've got so much infection in this country: over 50,000 cases at the moment. Just to put that in another context, that's 1% of the UK population. It's about one in a hundred people, even lower than that in some parts of the UK.

Linda - So if you then multiply, say when we're not in lockdown, I might have on average 10 contacts in that week. Um, and so you can see that that's what adds up the numbers. The government is talking about changing that. Singapore is also discussing this in some other countries. If we're going to live alongside COVID, particularly moving out of pandemic to endemic, we're still going to have people who test positive who might have to self isolate, but can we for their contacts, give them regular testing instead, so that we know whether they will develop the disease COVID-19 or not. Because actually most contacts of positive cases don't actually go on to develop it in these contact tracing systems. So let's look ahead. I don't think it's going to continue indefinitely, but for the moment that's the system that we have

Chris - Anyone been pinged on the panel?

Eleanor - Earlier. Not recently, luckily, I was very impressed by the lovely people who would call up and check in and check I had enough food and everything was okay. I was very impressed by the call handlers.

Chris - Ah so you got the phone call to say you'd been in contact. Did you actually get COVID or did you escape?

Eleanor - No, no, I didn't. No, I didn't. I didn't get COVID

Chris - But you did get reassuring phone calls about, are you alive?

Eleanor - Exactly, it was very reassuring.

Chris - I didn't realise they did that. That that's quite nice. Isn't it?

Linda - How did you find not being able to leave the house for 10 days then Eleanor? That's tough, isn't it?

Eleanor - Yeah, I found it very challenging and I live in a flat without a garden and that kind of thing. So I think it is very challenging psychologically, and I'm sure a lot of people have found that.

Richard - Does this mean that the pandemic, or is there a point where the pandemic becomes out of control or do you never want to say that? I mean, because test and trace can only work to a certain degree with a certain number of people. When you get certain number of cases, you can say, well you do, that whole idea of sort of let it rip through the population.

Linda - Yeah, well acutally in the UK's response, that was part of the story early on Richard, in that one of the reasons why the UK government didn't scale up contact tracing say last spring, in a way other countries does because they had so many infections early on, they just didn't think it would be viable. So when you do have a lot of infection, it's really difficult. It's easier to contact trace when you have far fewer numbers. So there's a big question about that. And we can see the performance of the system is taking longer for people to be identified. And just final point on this, on the pinging, a lot of people who are getting pinged now, they're not being advised to isolate for 10 days. They're being advised to isolate for say three, four or five days, because actually it's 10 days from the day they came in contact with the person who's positive. And if contact tracing is under strain it's taking longer to let the contacts know