The first cluster of coronavirus cases in Europe was officially detected on 21st February 2020 in Northern Italy, even if recent evidence showed sporadic first cases in Europe since the end of 2019. In this study, we have tested the presence of coronavirus in Italy and, even more importantly, we have assessed whether the virus had already spread sooner than 21st February. We use a counterfactual approach and certified daily data on the number of deaths (deaths from any cause, not only related to coronavirus) at the municipality level. Our estimates confirm that coronavirus began spreading in Northern Italy in mid-January.

中文翻译：

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冠状病毒何时到达欧洲？

欧洲的第一批冠状病毒病例于 2020 年 2 月 21 日在意大利北部正式发现，尽管最近的证据显示自 2019 年底以来欧洲出现了首例零星病例。在这项研究中，我们测试了意大利是否存在冠状病毒，并且，更重要的是，我们评估了病毒是否在 2 月 21 日之前就已经传播。我们使用反事实方法和经认证的每日死亡人数数据（由任何原因导致的死亡，不仅与冠状病毒有关）。我们的估计证实，冠状病毒于 1 月中旬开始在意大利北部传播。