On the Origin and Propagation of the COVID-19 Outbreak in the Italian Province of Trento, a Tourist Region of Northern Italy.

Luca Bianco,Nicola Segata,Paolo Lanzafame,Mattia Barbareschi,Lucia Collini,Andrea Silverj,Diego Micheletti,Mirko Moser,Annapaola Rizzoli,Massimo Pindo,Giovanni Lorenzin,Pietro Franceschi,Claudio Donati,Paolo Fontana,Omar Rota-Stabelli

doi:10.3390/v14030580

Abstract

Background: Trentino is an Italian province with a tourism-based economy, bordering the regions of Lombardy and Veneto, where the two earliest and largest outbreaks of COVID-19 occurred in Italy. The earliest cases in Trentino were reported in the first week of March 2020, with most of the cases occurring in the winter sport areas in the Dolomites mountain range. The number of reported cases decreased over the summer months and was followed by a second wave in the autumn and winter of 2020. Methods: we performed high-coverage Oxford Nanopore sequencing of 253 positive SARS-CoV-2 swabs collected in Trentino between March and December 2020. Results: in this work, we analyzed genome sequences to trace the routes through which the virus entered the area, and assessed whether the autumnal resurgence could be attributed to lineages persisting undetected during summer, or as a consequence of new introductions. Conclusions: Comparing the draft genomes analyzed with a large selection of European sequences retrieved from GISAID we found that multiple introductions of the virus occurred at the early stage of the epidemics; the two epidemic waves were unrelated; the second wave was due to reintroductions of the virus in summer when traveling restrictions were uplifted.

Highlights

The first case of infection by the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) virus was reported in China [1] in late December 2019
The first case of COVID-19 in the Province of Trento was reported on 2 March, followed in a few days by a widespread community transmission of the epidemic, with many of the early cases occurring in the winter sport area in the Dolomites mountain range
The number of reported cases remained low during the summer, and started to grow in early September into a second epidemic wave, which by mid-October had surpassed in size the first one

Summary

Introduction

The first case of infection by the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) virus was reported in China [1] in late December 2019. The virus rapidly spread globally, and the first indigenous case of COVID-19 was reported in Italy on February 2020 in the town of Codogno, Lombardy, followed by the first recorded Italian fatality attributed to COVID-19 on February 2020 in Vo’, Veneto. 2020 and was uplifted on 3 June 2020 During this first epidemic wave covering a three-month period between March and June, an estimated 226,970 people were diagnosed with COVID-19 infection in Italy, with 33,704 attributed casualties. Trentino is an Italian province with a tourism-based economy, bordering the regions of Lombardy and Veneto, where the two earliest and largest outbreaks of COVID-19 occurred in Italy. The number of reported cases decreased over the summer months and was followed by a second wave in the autumn and winter of 2020. Conclusions: Comparing the draft genomes analyzed with a large selection of European sequences retrieved from GISAID we found that multiple introductions of the virus occurred at the early stage of the epidemics; the two epidemic waves were unrelated; the second wave was due to reintroductions of the virus in summer when traveling restrictions were uplifted

Methods

Results

Discussion

Conclusion