key: cord-0923774-oc4js6wm
authors: Messali, Serena; Campisi, Giovanni; Giovanetti, Marta; Ciccozzi, Massimo; Caruso, Arnaldo; Caccuri, Francesca
title: The first Italian outbreak of SARS‐CoV‐2 B.1.1.7 lineage in Corzano, Lombardy
date: 2021-09-18
journal: J Med Virol
DOI: 10.1002/jmv.27333
sha: 30345fd3bc3e07fc3d158c3ffb0f08860aa38abd
doc_id: 923774
cord_uid: oc4js6wm

In December 2020, Italy experienced the first case of severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) B.1.1.7 lineage. In January 2021, we identified 21 cases of this variant in Corzano, defining the first outbreak of SARS‐CoV‐2 B.1.1.7 lineage in Italy. The high transmissibility of the B.1.1.7 variant represented an important benefit for the virus, which became rapidly dominant on the territory. Containment measures induced the epidemic curve onto a decreasing trajectory underlining the importance of appropriate control and surveillance for restraint of virus spread. Highlights The first Italian outbreak of SARS‐CoV‐2 B.1.1.7 lineage occurred in Lombardy in January 2021. The outbreak originated by a single introduction of the B.1.1.7 lineage. The genomic sequencing revealed, for the first time, the presence of the V551F mutation in the B.1.1.7 lineage in Italy. Surveillance, prompt sequencing and tracing efforts were fundamental to identify and to quickly contain the outbreak.

Since the first case of coronavirus disease 2019 (COVID-19), the continuous spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) across the world has allowed the virus to generate a large number of mutations leading to distinctive SARS-CoV-2 variants. Identification and tracing of these mutations through whole-genome sequencing have been critical from one side to characterize new variants that could alter the virologic and clinical features of the disease, and from the other side to map outbreaks within the population over time. The first variant that has rapidly expanded across European countries was initially detected in the UK and belongs to the B.1.1.7 lineage (20I/501Y.V1, also called a variant of concern [VOC] 202012/01). 1 In Italy, the first case of the B.1.1.7 variant was identified in December 2020 in a traveler who arrived from the UK. 2 Since then, the variant has been identified in different towns in Italy. 3 Close contacts from households, students, and teachers were instructed to self-isolate. In the subsequent days, massive COVID-19 testing was conducted. With the increasing number of SARS-CoV-2 infections within 10 days, an outbreak emergence status was declared and schools were closed. None of the infected individuals identified in this outbreak reported severe respiratory, but rather general, unspecific symptoms, such as fatigue, headache, back pain, or exhaustion. Only one of these individuals required nonintensive care unit hospitalization. In conclusion, the presence of the B.1.1.7 variant in Corzano posed critical challenges to epidemic control. Its higher transmissibility represented a strong selective advantage that makes it prone to rapidly become the dominant strain. Our survey analyses show that viral transmission could be effectively and rapidly suppressed by combining the early isolation of infected people with social distancing.

The authors declare that there are no conflict of interests. 

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The first Italian outbreak of SARS-CoV-2 B.1.1.7 lineage in Corzano, Lombardy