Before revision: We analyze social network data from Twitter to uncover early-warning signals of COVID-19 outbreaks in Europe in the winter season 2020 , before the first public announcements of local sources of infection were made.
After revision: We analyze social network data from Twitter to uncover early-warning signals of COVID-19 outbreaks in Europe in the winter season 2019-2020 , before the first public announcements of local sources of infection were made.