What is the impact of physical distancing guidelines on social contacts relevant for #COVIDー19 transmission? Our new @medrxivpreprint paper seeks to address this question for #USA, #UK, #Italy, #Germany, #Spain, #France, #Belgium, #Netherlands): https://www.medrxiv.org/content/10.1101/2020.05.15.20102657v1 1/7

We designed #CHBS, an online survey on @Facebook and collected data on the number of social contacts at home, school, work, and in other locations from March 12, 2020 onwards. Three are the key messages of our work: 2/7

1 - Social contact numbers mainly decreased after governments issued physical distancing guidelines rather than after announcing national lockdown measures. This is clear from data in #US, #UK, and #Germany. 3/7

2 - Compared to pre-COVID levels, the reduction in overall social contacts was between 48% (DE) and 85% (IT). Although smaller than observed in Wuhan, these reductions sufficed to bring the basic reproduction number R0 below one in almost all contexts considered. 4/7

The exceptions were DE and FR, for which we concluded that the reduction in social contacts had to be paired with strategies to decrease infection transmissibility to bring the R0 within the safety zone below one. 5/7

3 - Participants older than 65 years reported a larger reduction in social contacts than younger people, indicating relatively higher protection for more-at-risk groups. 6/7

Finally, I really want to thank the great multidisciplinary team behind the COVID-19 Health Behaviour Survey #CHBS: @cimentadaj @PerrottaDaniela @grow_andre @sof14g1l @chiccorampazzo @ezagheni and the staff at @MPIDRnews #epitwitter #poptwitter 7/7