SARS-CoV-2 introductions and early dynamics of the epidemic in Portugal

Portuguese network for SARS-CoV-2 genomics (Consortium): Agostinho José S Lira, Aida M Sousa Fernandes, Alexandra Estrada, Alexandra Nunes, Alfredo Rodrigues, Ana Caldas, Ana Constança, Ana Margarida Henriques, Ana Miguel Matos, Ana Oliveira, Ana Paula Dias, Ana Pelerito, Ana Rita Couto, Anabela Vilares, António Albuquerque, Baltazar Nunes, Bruna R Gouveia, Carina de Fátima Rodrigues, Carla Feliciano, Carla Roque, Carlos Cardoso, Carlos Sousa, Cathy Paulino, Célia Rodrigues Bettencourt, Claudia C Branco, Cláudia Nunes Dos Santos, Conceição Godinho, Constantino P Caetano, Cristina Correia, Cristina Toscano, Cristina Veríssimo, Daniela Silva, Diana Patrícia Pinto da Silva, Eliana Costa, Elizabeth Pádua, Fátima Martins, Fátima Vale, Fernanda Vilarinho, Fernando Branca, Filomena Caldeira, Filomena Lacerda, Francisca Rocha, Graça Andrade, Helena Ribeiro, Helena Rodrigues, Herberto Jesus, Hugo Sousa, Idalina Ferreira, Inês Baldaque, Inês Costa, Inês Gomes, Inna Slobidnyk, Isabel Albergaria, Isabel Dias, Isabel Fernandes, Isabel Lopes de Carvalho, Ivone Água-Doce, Jácome Bruges Armas, Joana Ramos, João Carlos Sousa, João Costa, João Dias, João Rodrigues, João Sobral, Jorge Machado, Jorge Meneses, José Alves, José Vicente Constantino, Laura Brum, Leonor Silveira, Líbia Zé-Zé, Lidia Santos, Ludivina Freitas, Luís Silva, Luisa Mota-Vieira, Lurdes Lopes, Lurdes Monteiro, Márcia Faria, Margarida Farinha, Margarida Vaz, Maria Alice Pinto, Maria Ana Pessanha, Maria Beatriz Tomaz, Maria Calle Vellés, Maria da Graça Maciel de Soveral, Maria Helena Ramos, Maria Isabel Veiga, Maria João Gargate, Maria João Peres, Maria José Borrego, Maria Matos Figueiredo, Mariana Martins, Mariana Viana, Maurício Melim, Miguel Babarro Jorreto, Miguel Fevereiro, Miguel Pinheiro, Mónica Oleastro, Nair Seixas, Nelson Ventura, Nuno Verdasca, Olga Costa, Patrícia Barros, Patricia Fonseca, Patricia Miguel, Paula Bajanca-Lavado, Paula Branquinho, Paula Palminha, Paula Soares, Paula Valente, Paulo Leandro, Paulo Pereira, Pedro Cardoso, Pedro Pechirra, Pedro Ramos, Raquel Neves, Raquel Rocha, Raquel Rodrigues, Raquel Sabino, Regina Sá, Ricardo Filipe Romão Ferreira, Ricardo Rodrigues, Rita C Veloso, Rita Cordeiro, Rita Côrte-Real, Rita de Sousa, Rita Gralha, Rita Macedo, Rita Matos, Rita Rodrigues, Sandra Paulo, Sara Sousa, Sílvia Lopo, Sónia Marta Santos Magalhães, Sónia Rodrigues, Sónia Silva, Susana Ladeiro, Susana Martins, Susana Silva, Teresa Salvado, Tiago Luís, Valquíria Alves, Vera ManageiroBackground: Genomic surveillance of SARS-CoV-2 in Portugal was rapidly implemented by the National Institute of Health in the early stages of the COVID-19 epidemic, in collaboration with more than 50 laboratories distributed nationwide. Methods: By applying recent phylodynamic models that allow integration of individual-based travel history, we reconstructed and characterized the spatio-temporal dynamics of SARS-CoV-2 introductions and early dissemination in Portugal. Results: We detected at least 277 independent SARS-CoV-2 introductions, mostly from European countries (namely the United Kingdom, Spain, France, Italy, and Switzerland), which were consistent with the countries with the highest connectivity with Portugal. Although most introductions were estimated to have occurred during early March 2020, it is likely that SARS-CoV-2 was silently circulating in Portugal throughout February, before the first cases were confirmed. Conclusions: Here we conclude that the earlier implementation of measures could have minimized the number of introductions and subsequent virus expansion in Portugal. This study lays the foundation for genomic epidemiology of SARS-CoV-2 in Portugal, and highlights the need for systematic and geographically-representative genomic surveillance.Plain language summary: Analysing SARS-CoV-2 genetic material and how it changes over time can help us understand how the virus spreads between countries and determine the impact of control measures. In this study, we investigated SARS-CoV-2 transmission and evolution in the early stages of the COVID-19 pandemic in Portugal. In particular, we reconstructed the routes and timeliness of viral introductions into the country and assessed the relative contribution of each introduction in terms of how the epidemic evolved over time. We detected at least 277 independent introductions, mostly from European countries (namely the United Kingdom, Spain, France, Italy, and Switzerland), which were consistent with the countries with the highest connectivity with Portugal. This study reflects an unprecedented effort in the field of the infectious diseases in Portugal, highlighting the need for systematic and geographically-representative surveillance to aid public health efforts to control the virus.This study is co-funded by Fundação para a Ciência e Tecnologia and Agência de Investigação Clínica e Inovação Biomédica (234_596874175) on behalf of the Research 4 COVID-19 call. Some infrastructural resources used in this study come from the GenomePT project (POCI-01-0145-FEDER-022184), supported by COMPETE 2020 - Operational Programme for Competitiveness and Internationalisation (POCI), Lisboa Portugal Regional Operational Programme (Lisboa2020), Algarve Por tugal Regional Operational Programme (CRESC Algarve2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), and by Fundação para a Ciência e a Tecnologia (FCT).