March 3, 2020, by Brigitte Nerlich

## Mathematical models, political decision making and public perceptions

On Tuesday, 3 March, Boris Johnson revealed the government’s action plan on how to deal with the novel coronavirus and the spread of Covid-19.

Despite doubts about the usefulness of experts expressed some years ago by some of his colleagues, he was flanked by experts, namely Sir Patrick Vallance, the Government Chief Scientific Adviser, and Professor Chris Whitty, the Government Chief Medical Adviser. They talked about various things, including mathematical modelling and how this was guiding policy on Covid-19. An immediate aim was to ‘flatten the curve‘ or to ‘stretch it’ or to ‘pull it down’, all paraphrases for reducing the peak of the epidemic in order to gain time for action. [Since I wrote this on Tuesday, flatting the curve has become something of a meme!, see here for example, tweet by @CT_Bergstrom; added Friday 6 March) (And here is the animated version, added Sunday 8 March)

I think there should have been a picture/graph (such as this titled ‘Press down firmly’ in The Economist) in the background so that people might have been able to visualise what he meant.

This reminded me of the way that policy was made during the foot and mouth disease outbreak in 2001 when Sir David King was the government’s chief scientist and the modelling was done, in effect, by many of the same people that are doing the modelling of Covid-19 now.

As some of you may remember, foot and mouth disease led to the slaughter of millions of animals and some of this slaughter policy was based on mathematical epidemiological modelling. Covid-19 is different of course, but when I re-read a paper I wrote after foot and mouth I thought we might want to keep an eye on how the models and the metaphors develop and how they might influence policy and public perception in the face of the real and visceral spread of the virus. Can we avoid the shift from positive to negative perceptions?

In 2007 I wrote the following in a paper entitled “Media, Metaphors and Modelling: How the UK newspapers reported the epidemiological modelling controversy during the 2001 foot and mouth outbreak”, reflecting on how the disease outbreak looked in the fields and on graphs:

“In one mode ‘the disease’ conjured up an array of medieval images of fire, hell and plague, in the other mode ‘the disease’ waxed and waned in two-dimensional graph space. In both modes of visuality the technology, i.e. the modelling, became itself invisible; what remained visible were on the one hand its results in the form of policies which themselves were transformed into actions and finally into dead bodies and on the other its results in the form of graphs.”

I then quoted some newspaper paragraphs to illustrate this ‘graphing’ of the disease:

“Culling infected animals within 24 hours of a positive diagnosis on a farm and killing all animals on neighbouring farms within 48 hours could result in the epidemic peaking within the next seven days, Professor King said”; “The 24/48-hour policy introduced on the 22 March appears to have stopped the exponential increase in the epidemic, with new cases following a diminishing curve that is set almost to peter out by the time of an expected June election. Professor King said: ‘Nobody is saying that this epidemic can just be switched off…’; “The government’s chief scientific adviser, Professor David King, said on Wednesday that the epidemic was ‘flattening out‘; “If the models were accurate, the number of new cases would tail off over the summer.”

I went on to say: “The clash between war-like imagery on the ground and graph imagery in the sphere of policy might have contributed to gradually shifting the value of the images associated with the modelling exercise from positive to negative.”