The pandemic of the COVID-19 disease caused by the SARS-CoV-2 virus has been believed to originate in China and spread later to other parts of the world. It is well acknowledged that the first diseased individuals appeared in China as early as in December 2019, and possibly even earlier in November. It has also been well established that the virus stroke Italy later in January or in February 2020, distinctly after the outbreak in China. Paper by Apolone et al. published in a local Italian medical journal in November 2020 however exposed this chronology to doubt. By fitting early part of the epidemic curve with the exponential model and extrapolating it backwards in time, we could estimate the day-zero of the epidemic and calculated its confidence intervals in Italy and China. We also calculated how probable it is that Italy encountered the virus prior 1 January 2020. We determined an early portion of the epidemic curve representing unhindered exponential growth which fit the exponential model with high determination >0.97 in both countries. We suggest that the day-zero in China and Italy was 8 December (95% CI: 3 December, 20 December) and 22 January (95% CI: 16 January, 29 January), respectively. We could with high confidence reject that Italy encountered the virus earlier than China (p<0.01). Based on our analysis we oppose the findings published by Apolone at al. and view the proposed pre-pandemic presence of the virus in Italy as very unlikely.
Published Date: 2021-09-23; Received Date: 2021-09-02