Poggiali E, Vercelli A, Vadacca GB, et al. Negative nasopharyngeal swabs in COVID-19 pneumonia: the experience of an Italian Emergengy Department (Piacenza) during the first month of the Italian epidemic. Acta Biomed. 2020;91(3):e2020024. doi:10.23750/abm.v91i3.9979