A simple equation has changed the way that we live. It is having a greater impact than any of the ground breaking theories from science. The reproduction number \(R\) is being used to change our behaviours to reduce the spread of the Covid-19 virus and will leave its mark on us well into the future.
Governments around the world are using \(R\) to guide their actions in controlling the spread of the Covid-19 virus. The version of \(R\) that they are using is the “basic” reproduction number, \(R_0\) ( or \(R\) nought) and it is the situation when when no one has been vaccinated, no one has had the disease before and there is no way to control the disease. Calculating \(R\) is a complicated process but comes down to three components: how long a person is infected, how often they come in contact with others and how the disease is spread. A long period of infection will increase the value of \(R\). If a person comes in contact with lots of people then they increase the value of \(R\) as well as how it is transmitted for example airborne diseases will give a higher value.
The value of \(R\) is used to assess the contagiousness of a disease. For example if \(R\) has a value of 2 then one infected person will pass the virus onto another two other people who in turn will each pass it onto another two and so on. If \(R\) is less than 1 then the spread of the virus will decline. Calculating $R$ requires complex mathematical modelling, lots of data and powerful computers which results, at best, in an average for its value. For example $R$ has a value of between 1 - 2 for the common cold, SARS is 2 - 5, and at the early stages of Covid-19 it varied between 1.4 - 5.7. The UK Government’s action plan is aimed at reducing \(R\) by breaking the transmission of the virus with regular messages by washing hands, enforcing social distancing and a lockdown for non-essential workers. Early signs, but unconfirmed, is that \(R\) could be between 1 and 0.5
But it is the impact of reducing \(R\) which is having a dramatic impact on our lives. Health and Social Care systems are having to respond to the virus in ways that were never expected as they fight to save as many lives as possible. Non-essential parts of the UK economy have hit a brick wall while other sectors plummeted to their lowest levels of activity since records began. There is a similar picture around the world which is slowing global trade and will ultimately reduce economic activity in national economies. The response of governments to the pandemic is starting to raise fundamental questions about how we live and work. How will those people who are identified as key workers be valued in the future by society? Will government intervention in the economy during the crisis remain for many years ahead? Is their proposed tracking and tracing app a step too far in monitoring society? How much do we really know about the human body and how it works and how its it translated into medicine Will the growth of the digital economy accelerate through on-line entertainment and delivering more goods to our doorsteps but will it go on to change the type of work? Are the days of commuting over? Will on-line learning become an integral part of education? Will the remote monitoring and support of patients be a few clicks from a doctors desk? Should the length of supply chains be reduced to within our shores and we make more of our own products so that we can respond quickly to future crisis?
If \(R\) had stayed buried in technical papers and and discussed in specialist conferences with the occasional discussion at a government strategic committee then we would never of heard of it. But now it has made its way into everyones lives, through the actions of governments, then lots of questions are bubbling to the surface. The longer that the fight against Covid-19 goes on then the greater the public will require action in answering these questions.
Over a century ago Einstein’s equation \(E=mc^2\) was brought to the publics attention which heralded the start of a revolution in our understanding of how the universe works, from planets down to the quantum level, which created the technology that has shaped our lives. \(R\) has signalled the start of another science revolution but this time it will be in our understanding of how we live together and down to the level cell activity s which will change our future.