Quantifying the impact of physical distance measures on the transmission of COVID-19 in the UK

Christopher I Jarvis; Kevin Van Zandvoort; Amy Gimma; Kiesha Prem; Petra Klepac; G James Rubin; W John Edmunds

The measures introduced by the UK Government appear to have high levels of uptake among participants and have resulted in very large (73%) reductions in the total number of contacts. If similar changes are observed across the UK population, we would expect the basic reproduction number to now be below 1 (0.62; 95% CI 0.37 -0.89), and that these physical distancing measures will lead to a decline in cases in the coming weeks. However, this projected decline in incidence will not result in an immediate decline in reported cases, as there are significant delays between infection and the onset of symptomatic disease and hospitalisation, as well as further delays to these events being reported. Hence, routine surveillance data are unlikely to show a decline in cases for some time. However, by directly measuring individuals' contact patterns and estimating the corresponding basic reproduction number, we are able to rapidly quantify the impact of physical distancing on transmission.