Italy welcomed and incubated the traveler SARS-CoV-2 upon its arrival from China, and has unwittingly contributed to its spread to the rest of Europe. This is a known story, but now an Italian study published in Nature reconstructs the first fundamental steps in the spread of the new coronavirus in the boot between January and February 2020, when the infections added up in Lombardy and Veneto and people still persisted in talking about “virus Chinese”.
SARS-Cov-2 arrives in Italy. This is the photograph returned by the study of the SCIRE group (SARS-CoV-2 Italian Research Center), coordinated by Alessia Lai, biologist of the Department of Biomedical and Clinical Sciences of the Milanese hospital “Luigi Sacco” (State University: Alessia Lai is the head of the team that first isolated the Italian coronavirus strain), which also includes Andrea Crisanti, Massimo Galli and Gianguglielmo Zehender.
From china: two forms of the virus. The SARS-CoV-2 arrives in Italy in two different “introductions”, that is to say through two different channels, one with Veneto as its destination and one with Lombardy as its destination. Already at this first moment, in the first weeks of 2020, the virus has two different forms originated in China (and which did not separate after arriving in Italy). One of them, renamed B, arrives in Veneto and remains there as in a siding: the infections remain limited and the outbreak is extinguished. The other, B.1, lands in Lombardy where the virus multiplies and begins to spread.
from Lombardy towards the lockdown. The B.1 lineage, the scientists write, spreads from Lombardy to other Italian regions (Veneto, Emilia Romagna, Abruzzo, Marche, Puglia, Friuli Venezia Giulia and Lazio). From Abruzzo, the virus further mutated into a new lineage, B.1.1, spreads again in Veneto and Lombardy, then in Sardinia and Puglia. Meanwhile, SARS-CoV-2 has gained the D614G mutation, which promotes its transmissibility and travels at full speed. Another version, called B.1.1.1, probably develops in other European countries and returns to Italy only in the second half of March, remaining located in Piedmont: it will remain confined here, because by now the entire peninsula has entered into lockdown. .
Italy was not only the first country in addition to China to register a devastating epidemic wave of covids, but it can also be considered one of the main spreading hubs of SARS-CoV-2 in Europe and the United States. The reconstruction of the scientists is based on thephylogenetic analysisthat is, as Zehender explained some time ago a Focus.it, «The study on the comparison of the genomes of isolated viruses, the sequences of which have been deposited in publicly accessible databases. Imagining the results of phylogenetic analyzes as a tree, the genome sequences of Chinese viruses are the basis: they are the roots ». Those we are talking about now, in this reconstruction, are instead the first ramifications: they are what researchers call “ancestral lineages”.
Since the virus continuously accumulates mutations, by studying backwards the succession of these changes it is possible to reconstruct the evolutionary history of SARS-CoV-2 with its transformations over time.