Italian version of the baseline questionnaire in use between 16 December 2020 and 19 January 2021 assessing self-reported sociodemographic characteristics, lifestyle, health status, anthropometry as well as SARS-CoV-2 testing, symptoms related to SARS-CoV-2 infection, and contact with infected or symptomatic individuals. Changes to the previous version: The SARS-CoV-2 testing section was redefined and a symptoms duration question was added.