Optimizing COVID-19 surveillance in long-term care facilities: a modelling study oleh David R. M. Smith, Audrey Duval, Koen B. Pouwels, Didier Guillemot, Jérôme Fernandes, Bich-Tram Huynh, Laura Temime, Lulla Opatowski, on behalf of the AP-HP/Universities/Inserm COVID-19 research collaboration