Behavioral changes before lockdown and decreased retail and recreation mobility during lockdown contributed most to controlling COVID-19 in Western countries

Abstract

BackgroundThe COVID-19 pandemic has prompted a lockdown in many countries to control the exponential spread of the SARS-CoV-2 virus, hereby reducing the time-varying basic reproduction number ( R t ) to below one. Governments are looking for evidence to balance the demand of their citizens to ease some of the restriction, against the fear of a second peak in infections. More details on the specific circumstances that promote exponential spread (i.e. R t > 1) are needed.MethodsIncidence data of cases and deaths from the first wave of infections for 35 Western countries (32 European, plus Israel, USA and Canada) were analyzed using epidemiological compartment models in a Bayesian framework. Mobility data was used to estimate the timing of changes associated with a lockdown, and was correlated with estimated reductions of R t .ResultsAcross all countries, the initial median estimate for R t was 3.6 (95% IQR 2.4 – 5.2), and it was reduced to 0.78 (95% IQR 0.58 – 1.01) during lockdown. 48% (18% – 65%) of the reduction occurred already in the week before lockdown, with lockdown itself causing the remaining drop in transmission. A lower R t during lockdown was independently associated with an increased time spent at home (0.21 per 10% more time, p < 0.007), and decreased mobility related to retail and recreation (0.07 per 10% less mobility, p < 0.008).ConclusionsIn a Western population unaware of the risk, SARS-CoV-2 can be highly contagious with a reproduction number R 0 > 5. Our results are consistent with evidence that recreational activities (including restaurant and bar visits) enable super-spreading events. Exiting from lockdown therefore requires continued physical distancing and tight control on this kind of activities.

The association of community mobility with the time-varying reproduction number (R) of SARS-CoV-2: a modelling study across 330 local UK authorities

“…Our findings suggest that increased visits to retail and recreation places, such as non-essentials shops, restaurants, and cinemas, might have contributed to the increased SARS-CoV-2 transmission nationwide; by comparison, essential visits to grocery and pharmacy stores were only associated with a small increase in transmission. Similar findings were reported by Deforche and colleagues, 13 who showed that decreased retail and recreation mobility contributed most to reduced COVID-19 epidemics in 35 high-income countries. These findings might justify the need to focus on non-essential recreation activities to reduce transmission.…”

Exit strategies from lockdowns due to COVID-19: a scoping review

“…A UK-based modelling study [ 86 ] examined the effect of opening schools along with removing restrictions on different occupation groups and concluded increased transmission, i.e., R0 above one (the basic reproduction number, R0 is the average number of secondary infections produced by a typical case of an infection in a population where everyone is susceptible [ 12 ]). Continued restriction on recreational activities (e.g., restaurants and bars) during exiting has been suggested in a modelling study based in high-income countries [ 87 ].…”