Even before public announcements of the first cases of COVID-19 in Europe were made, at the end of January 2020, signals that something strange was happening were already circulating on social media. A new study of researchers at IMT School for Advanced Studies Lucca, published in Scientific Reports, has identified tracks of increasing concern about pneumonia cases on posts published on Twitter in seven countries between the end of 2019 and the beginning of 2020. The analysis of the posts shows that these warnings came from the exact geographical regions where the primary outbreaks later developed.