Timeline of SARS-CoV2 spread in Italy: results from an independent serological retesting

ABSTRACT

The massive emergence of COVID19 cases in the first phase of pandemic within an extremely short period of time suggest that an undetected earlier circulation of SARS-CoV-2 might have occurred, as documented by several papers in different countries, including a few that reported positive cases even earlier the first cases identified in Wuhan. Given the importance of this evidence, an independent evaluation was recommended. Here we report the results of SARS-CoV-2 antibodies blind retesting of blood samples collected in the prepandemic period in Italy, and in control samples collected one year before, by two independent centers. Results suggest the presence of SARS-CoV-2 antibodies in some samples collected in the prepandemic period, though the detection of IgM and/or IgG binding and neutralizing antibodies is strongly dependent on the different serological assays and thresholds employed, while being absent in control samples collected one year before. These findings highlight the importance of harmonizing serological assays for testing SARS-CoV-2 virus spreading and may contribute to a better understanding the future virus dynamics. Article Summary LineWe report the results of an independent retesting of SARS-CoV-2 antibodies in blood samples collected in prepandemic period in Italy and in matched samples collected one year before. The findings indicate the presence of IgM and/or IgG antibodies in selected samples of the prepandemic period only with different performance of serological assays used by the two centers. The results could give highlights on SARS-CoV-2 circulation in the pre-pandemic period and contribute to better predict future virus dynamic.