Before revision:  Specifically, the intensity of COVID-19 related social media activity from different Italian, Spanish and United States regions at the beginning of the epidemic, predicts well the total number of deaths reached almost a month later in each region. More strikingly, at the time of the initial twitter reaction no tabled regional data on the epidemic was readily available in Italy. By the 24th February 2020 only two regions reported death cases and only three reported infected subjects. Our findings could underpin the creation of real-time novelty detection systems aimed at early reporting of SARS-like mortality and thus early activation of control measures in future pandemics .
After revision:  Specifically, the intensity of COVID-19 related social media activity from different Italian, Spanish and United States regions at the beginning of the epidemic, predicts well the total number of deaths reached almost a month later . Our findings suggest that "the crowds" perceived the risk correctly. This is one of the few examples where the "wisdom of crowds" can be quantified and applied in practice. This can be used to create real-time novelty detection systems aimed at early reporting of SARS-like mortality and thus early activation of control measures in future pandemics .