Dissemination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in healthcare institutions affects both patients and health-care workers (HCW), as well as the institutional capacity to provide essential health services. Here, we investigated an outbreak of SARS-CoV-2 in a “non-COVID-19” hospital ward unveiled by massive testing, which challenged the reconstruction of transmission chains. The contacts network during the 15-day period before the screening was investigated, and positive SARS-CoV-2 RNA samples were subjected to virus genome sequencing. Of the 245 tested individuals, 48 (21 patients and 27 HCWs) tested positive for SARS-CoV-2. HCWs were mostly asymptomatic, but the mortality among patients reached 57.1% (12/21). Phylogenetic reconstruction revealed that all cases were part of the same transmission chain. By combining contact tracing and genomic data, including analysis of emerging minor variants, we unveiled a scenario of silent SARS-CoV-2 dissemination, mostly driven by the close contact within the HCWs group and between HCWs and patients. This investigation triggered enhanced prevention and control measures, leading to more timely detection and containment of novel outbreaks. This study shows the benefit of combining genomic and epidemiological data for disclosing complex nosocomial outbreaks, and provides valuable data to prevent transmission of COVID-19 in healthcare facilities.

Background. Dissemination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in healthcare institutions affects both patients and health-care workers (HCW), as well as the institutional capacity to provide essential health services. Methods. We conducted an investigation of a cluster of SARS-CoV-2 positive cases detected in a 'non-COVID-19' hospital ward during Summer 2020. The magnitude of the nosocomial outbreak was disclosed by massive testing, challenging the retrospective reconstruction of the introduction and transmission events. An in-depth contact tracing investigation was carried out to identify the contacts network during the 15-day period before the screening. In parallel, positive SARS-CoV-2 RNA samples were subjected to virus genome sequencing. Results. Of the 245 tested individuals, 48 (21 patients and 27 HCWs) tested positive for SARS-CoV-2. HCWs were mostly asymptomatic, but the mortality among the vulnerable patient group reached 57.1% (12/21). Phylogenetic reconstruction revealed that all cases were part of the same transmission chain, thus confirming a single origin behind this nosocomial outbreak. By combining vast epidemiological and genomic data, including analysis of emerging minor variants, we unveiled a scenario of silent SARS-CoV-2 dissemination within the hospital ward, mostly driven by the close contact within the HCWs group and between HCWs and patients. This investigation triggered enhanced prevention and control measures, leading to a more timely detection and containment of novel nosocomial outbreaks. Conclusions. The present study shows the benefit of combining genomic and epidemiological data for the investigation of complex nosocomial outbreaks, and provides valuable data to minimize the risk of transmission of COVID-19 in healthcare facilities.

A pandemia COVID-19 implicou alterações no funcionamento do sistema de saúde, com interrupção da atividade clínica programada, que, associada ao receio pelos doentes do risco de contaminação, condicionou o atendimento médico. No presente artigo analisámos os dados da atividade nos centros de Cardiologia dos hospitais CUF Infante Santo e CUF Porto durante o estado de emergência nacional. Estes hospitais, com características semelhantes na multifuncionalidade cardiovascular e integrados nos centros para tratamento da COVID-19, tiveram uma redução superior a 70% nas consultas presenciais, ultrapassando os 60% para a quase totalidade dos exames complementares de diagnóstico, em comparação com o período homólogo de 2019. Estes valores foram mais acentuados na evolução do primeiro quadrimestre de 2020, sobretudo à custa de atividade residual em abril. Os procedimentos invasivos eletivos também diminuíram, apresentando uma queda mais marcada em abril. No entanto, as intervenções urgentes por síndroma coronária aguda mantiveram-se sem variação face a igual período de 2019. Reforça-se a necessidade de divulgar a importância de recorrer às urgências hospitalares e da manutenção das normas de segurança na retoma gradual da atividade, e aborda-se o papel crescente da telemedicina e assistência domiciliária, bem como da reorganização do funcionamento das equipas hospitalares para melhorar a dinâmica multidisciplinar nas várias componentes da Cardiologia.