Digital SARS-CoV-2 Detection Among Hospital Employees: Participatory Surveillance Study - Onicio Leal-Neto; Thomas Egger; Matthias Schlegel; Domenica Flury; Johannes Sumer; Werner Albrich; Baharak Babouee Flury; Stefan Kuster; Pietro Vernazza; Christian Kahlert; Philipp Kohler (JMIR Public Health and Surveillance, 2021)