Modelling: the UK's coronavirus strategy explained

24 March 2020

Interview with 

Freya Jephcott, University of Cambridge

BIG_BEN

A view of Big Ben and the top of Elizabeth Tower, with Boadicea in the foreground.

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There's a foundation of science underpinning the UK - and other nation’s - strategies to control the outbreak. The governments of these countries are relying heavily on mathematical models, including work by a team from Imperial College London. Freya Jephcott at the University of Cambridge independently studies how diseases spread, and Chris Smith asked her what those models are saying...

Freya - Right now we're moving towards something called suppression. So that model that Imperial made to feel out all these different possible scenarios came up with two key scenarios for us. One was when we do something called mitigation, which is where we try and slow the spread of the outbreak; that's where all that discussion of flattening the curve has come from. And then the other scenario, scenario B, is the suppression strategy; where we essentially try and just block transmission altogether through some more extreme social distancing interventions. This comes down to three key elements: home isolation for people with any signs of respiratory illness and isolation of all their household members, and that's for two weeks; and the other elements that have come in here is social distancing of the whole population. Now what that actually means was this idea that all of our contacts outside of work and school and the household would reduce by three quarters. Going to the pub, seeing friends, going to coffee shops; all of these interactions would dramatically reduce. Also workplace rate, so the amount that adults are mixing at work; that this would reduce by at least a quarter. They did allow that our household contacts, if we do this, were going to increase by a quarter. So there's a bit of an offset there. And the final element was either partial or full closures of schools and universities, and this seems to be the thing that's coming to the fore right now: this idea that we're going to close school to some children. Now one of the big concerns earlier on when this was discussed is that something like a third of our nurses, or healthcare workers in general, actually have school-age children; and that we're doing all these things to try and reduce the strain on our health system in the coming months, and that perhaps we might actually be making staff shortages worse if we do this. So it looks like the government has come to a strategy where people who have children, people who work in what are considered essential services - so healthcare, groceries, police, firefighters - their children will still attend school.

Chris - The overriding aim is to reduce contact between people because that is how the disease spreads. So if you reduce the contact between the people, you reduce the opportunities for transmission, and therefore we must by default slow down the spread, the rate at which it's transmitting through the population.

Freya - Absolutely. That's it. So everything we're doing now is to try and reduce the number of opportunities for new people to get infected with the virus, even if they're not confirmed cases. And so we're doing that by trying to reduce social contacts generally. Though we've gone from trying to just slow it, to actually now the strategy is to try and sort of stamp it out almost entirely for now.

Chris - Do you think that is likely to be achieved?

Freya - The reason we think it might be possible: in China - and they do have a lot more infrastructure and was a lot more compulsory than anything you'd bring in here - it does seem to have significantly reduced transmission, to the point where maybe there's very, very little community transmission going on now. South Korea similarly, they took a slightly different approach there, but again with this extreme social distancing. And they're seeing a bit of an uptick in cases, but otherwise they did bring down the community transmission dramatically. The catch here is that with this strategy, if we began to loosen these quite extreme measures, there is a good chance that we could see a big uptick in cases again.

Chris - If everyone did this all at the same time for a period of time, would it just disappear? Is it just the fact that at the moment, if any one country loosens its grip, it will just get this thing coming back; and we can be really diligent here in the UK, but if say a third world country which doesn't have the ability to implement these sorts of strategies acts as a sort of nidus or a hotbed for this, it'll just seed it back into everywhere that's very successfully stamped it out?

Freya - Absolutely. We are all in this together and we're only as strong as our weakest part. We need basic infrastructure so these kinds of interventions are possible globally, because like I said we can stamp it out in countries with the infrastructure, but as soon as we loosen it, we will get imported cases and we will get transmission starting again.

Chris - And just finally Freya, where do you think - and I realise I'm putting you horribly on the spot - but where do you think this is going to end, and how?

Freya - If we did absolutely nothing, it sounds like we would have hit peak cases and peak deaths within the next three months. So that would be quite a short ending but quite a bad ending. So I think that actually we're looking at this unfolding over months and years. The interventions that Imperial College suggested: in their models they lasted for about five months. If you hear the discussions of vaccines, that's still maybe a year, 18 months at best, away. It is worth keeping in mind that we're in this for the long haul and we need to think about interventions and policies for the distant future.

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