For those interested in the relationship between the Covid-19 pandemic and social networks, may I point out this new paper based upon Twitter and published on "Scientific Reports" yesterday: Early warnings of COVID-19 outbreaks across Europe from social media, https://www.nature.com/articles/s41598-021-81333-1 Abstract: "We analyze 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. We show evidence that unexpected levels of concerns about cases of pneumonia were raised across a number of European countries. Whistleblowing came primarily from the geographical regions that eventually turned out to be the key breeding grounds for infections. These findings point to the urgency of setting up an integrated digital surveillance system in which social media can help geo-localize chains of contagion that would otherwise proliferate almost completely undetected." Regards, MM -- Monica Marra INAF - Istituto Nazionale di Astrofisica Osservatorio di Astrofisica e Scienza dello Spazio v. Gobetti 93/3 I-40129 Bologna, Italy uff. 3W1 Scopus author ID: 7102382905 https://www.researchgate.net/profile/Monica_Marra