From 24 December 2020 to 8 February 2021, 163 cases of SARS-CoV-2 Alpha variant were identified in Chieti province, Abruzzo region. Epidemiological information allowed the identification of 14 epi-clusters. With one exception, all the epi-clusters were linked to the town of Guardiagrele: 149 contacts formed the network, two-thirds of which were referred to the family/friends context. Real data were then used to estimate transmission parameters: according to our method, the calculated Re(t) was higher than 2 before the 12 December 2020. Similar values were obtained from other studies considering Alpha variant. However, results should be critically interpreted in light of the epidemiological situation and control measures in place in the studied area at that particular time. Italian sequence data were combined with a random subset of sequences obtained from GISAID database. Genomic analysis showed close similarity between the sequences from Guardiagrele, forming one distinct clade. This would suggest one or limited unspecified introductions from outside to Abruzzo region in early December 2020, which led to the diffusion of Alpha in Guardiagrele and in neighbouring municipalities, with very limited inter-regional mixing.
Epidemiological and genomic findings of the first documented Italian outbreak of SARS-CoV-2 Alpha variant