Analysis of human mobility in the UK during the COVID-19 pandemic

Our aim is to assess the effects of the COVID-19 restriction measures on the mobility patterns of people in the UK. These measures are strong public health policies which came into place as a consequence of the COVID-19 pandemic and its potential impact on the British population and on the NHS. To do so, we analyse changes in the average levels of mobility of anonymous mobile phone users across the country at different time periods, which include the periods when the restriction measures are in place and enforced by authorities. Introduction This report presents our initial analysis of the restriction measures and their effect on mobility across the UK. This might be of interest to epidemiologist who can use this to estimate contact matrices, and to public health policy makers who have to assess the impact of their policies on the British population. This report builds on the rapidly growing body of work on the COVID19 pandemic1–10 and extends it to the UK scenario. This report is a working paper, which will be expanded and updated regularly. Our preliminary results can be summarised as follows: • In early March, before restriction measures were enforced, mobility levels decreased by about 10% compared to their normal levels before the pandemic. • In the middle of March, after people were encouraged to work from home and reduce their travelling, mobility levels dropped by about 50% compared to before the pandemic. • From March 24th onwards the UK entered a state of lockdown, with only essential travelling allowed. This led to a reduction of about 70% in the mobility levels. • Mobility levels have dropped consistently in all areas across the UK after the lockdown measurements. These results present our initial analysis of the restriction measures and their effect on mobility across the UK. This might be of interest to epidemiologist who can use this to estimate contact matrices, and to public health policy makers who have to assess the impact of their policies on the British population. Timeline of COVID-19 development in the UK In January 2020, cases of the novel coronavirus started being reported outside of China. These cases were typically from people who had recently travelled to the Chinese Hubei province, where the disease started spreading. Events related to COVID-19 in the UK started unfolding at the end of January, with the first reported cases in the country. A brief timeline for the UK is the following: 31/01/2020 : two Chinese nationals, one of whom studied at the University of York, were the first confirmed cases in the UK. 06/03/2020 : a man in Brighton became the third confirmed case in the UK. He had previously travelled to Singapore and then visited a ski resort in France. 10/03/2020 : the number of confirmed cases in the UK increases to 10, due to infections linked to the man in Brighton. 27/03/2020 : the total number of confirmed cases is 16, with the first sign of infections spreading from the outbreak in Northern Italy due to people travelling back from the affected regions. 01/03/2020 : the official number of cases is 36, and there are signs of infections amongst people with no history of recent travel abroad. 11/03/2020 : the confirmed cases in the UK are now 456. The World Health Organisation declares the outbreak a pandemic. 12/03/2020 : the UK Chief Medical Office raises the risk from moderate to high. Anyone with a new continuous cough or a fever is recommended to self-isolate for seven days, schools cancel trips abroad and people over 70 are asked to avoid cruises. 13/03/2020 : many sporting events are postponed, as well as the 2020 UK local elections. 16/03/2020 : the number of cases is over 1,500, and the number of deaths is 55. The Prime Minister advises against non essential travelling, and encourages people to avoid pubs, clubs and theatres. Working from home is encouraged. 23/03/2020 : the Prime Minister announces stricter measures for the UK coming into place from the following day (March 24th). People are asked to stay home except for essential food shopping, essential work travel and one form of exercise per day only with members of their household. 26/03/2020 : the death toll is 422, and the number of people that tested positive is 11,568. 27/03/2020 : both the Prime Minister and the Health Secretary announce testing positive for the virus. Note that this timeline is not meant to be complete, but is only an indication of how major events related to COVID-19 unfolded in the UK over time, and which restrictions were put into place at what point in time. For a more complete report on the development of COVID-19 in the UK, you can11. The Analysis Baseline February 2020 A key indicator to evaluate the effectiveness of these restrictions and assess the compliance of the population is the reduction in mobility. Here, we will use a large, national-scale data set on human mobility, provided by the collaboration with Cuebiq, to evaluate the adherence to these measures by the general population. These reports are based on similar analyses carried out on Italian data9 and US data10. We aim to provide and assess the changes in commuting and mobility at local authority level across UK during the COVID-19 health crisis. In order to assess whether movement of people has reduced in the UK during the restriction measures, we first have to establish what the regular level of movement across country is. We refer to this as our baseline. We use the radius of gyration12 as our measure of mobility. The radius of gyration provides an indication of the characteristic distance travelled by a person during a given time period. We estimate our baseline by considering the average mobility during the period between 01 and 04 of February 2020. This period is before restriction measures were put into place by the British government, and does not contain significant events, such as bank holidays or festivities, that may affect our baseline estimates. For our baseline, we use the median radius of gyration labeled as Degree of Mobility. Figure 1(A) depicts the results of our baseline estimates at local authority level. As an example of a comparison between the baseline and another day, we selected the 22nd of February and showed the comparison result in Figure 1(B). In the figure, the Mobility Activity represents the percentage of user mobility with respect to the baseline; a value of 100% indicates that the mobility is the same as the baseline, whereas lower values of mobility activity represent a reduction in the mobility of people in that area. We do not report values higher than 100% as they are not of interest for this analysis.