The COVID-19 pandemic has compelled public authorities to establish preventive measures involving individual behaviour modification strategies (mask-wearing, social distancing, etc.) with a view to community protection. In this context, documenting people's behaviour changes, the impact of public health measures, and individuals' knowledge, motivations, and beliefs – even their perception of how the crisis is being managed – is essential for understanding the experience of the population and adapting the management approach accordingly. This article presents findings and lessons on how to monitor a population's behaviour during a crisis, obtained by reviewing forty-five surveys conducted in Belgium and France during the first Covid-19 stay-at-home order, from April to May 2020. The central message is to argue that the citizens' role in this type of survey – and in managing the crisis, more generally – should be reconsidered by thinking of them as true health partners and members of a community that could be mobilised to help. [ABSTRACT FROM AUTHOR]