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Co-circulation of SARS-CoV-2 Alpha and Gamma variants in Italy, February and March 2021.
Stefanelli, Paola; Trentini, Filippo; Guzzetta, Giorgio; Marziano, Valentina; Mammone, Alessia; Sane Schepisi, Monica; Poletti, Piero; Molina Grané, Carla; Manica, Mattia; Del Manso, Martina; Andrianou, Xanthi; Ajelli, Marco; Rezza, Giovanni; Brusaferro, Silvio; Merler, Stefano.
  • Stefanelli P; Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
  • Trentini F; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Guzzetta G; Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy.
  • Marziano V; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Mammone A; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Sane Schepisi M; Directorate General of Health Prevention, Ministry of Health, Rome, Italy.
  • Poletti P; Directorate General of Health Prevention, Ministry of Health, Rome, Italy.
  • Molina Grané C; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Manica M; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Del Manso M; University of Trento, Trento, Italy.
  • Andrianou X; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
  • Ajelli M; Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
  • Rezza G; European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
  • Brusaferro S; Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
  • Merler S; Cyprus University of Technology, Limassol, Cyprus.
Euro Surveill ; 27(5)2022 02.
Article in English | MEDLINE | ID: covidwho-1700766
ABSTRACT
BackgroundSeveral SARS-CoV-2 variants of concern (VOC) have emerged through 2020 and 2021. There is need for tools to estimate the relative transmissibility of emerging variants of SARS-CoV-2 with respect to circulating strains.AimWe aimed to assess the prevalence of co-circulating VOC in Italy and estimate their relative transmissibility.MethodsWe conducted two genomic surveillance surveys on 18 February and 18 March 2021 across the whole Italian territory covering 3,243 clinical samples and developed a mathematical model that describes the dynamics of co-circulating strains.ResultsThe Alpha variant was already dominant on 18 February in a majority of regions/autonomous provinces (national prevalence 54%) and almost completely replaced historical lineages by 18 March (dominant across Italy, national prevalence 86%). We found a substantial proportion of the Gamma variant on 18 February, almost exclusively in central Italy (prevalence 19%), which remained similar on 18 March. Nationally, the mean relative transmissibility of Alpha ranged at 1.55-1.57 times the level of historical lineages (95% CrI 1.45-1.66). The relative transmissibility of Gamma varied according to the assumed degree of cross-protection from infection with other lineages and ranged from 1.12 (95% CrI 1.03-1.23) with complete immune evasion to 1.39 (95% CrI 1.26-1.56) for complete cross-protection.ConclusionWe assessed the relative advantage of competing viral strains, using a mathematical model assuming different degrees of cross-protection. We found substantial co-circulation of Alpha and Gamma in Italy. Gamma was not able to outcompete Alpha, probably because of its lower transmissibility.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Prognostic study / Randomized controlled trials / Risk factors Topics: Variants Limits: Humans Country/Region as subject: Europa Language: English Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: 1560-7917.Es.2022.27.5.2100429

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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Prognostic study / Randomized controlled trials / Risk factors Topics: Variants Limits: Humans Country/Region as subject: Europa Language: English Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: 1560-7917.Es.2022.27.5.2100429