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This st udy aims to evaluate the prevalence of SARS-CoV-2 antibodies in locked-down family households to determine viral dynamics and immunity acquisition. COVID-19 individuals and their households in lockdown under the same roof during early spring 2020 were interviewed and tested using rapid immunochromatographic lateral flow antibodies assays (LFA) between July and September 2020. Outcomes were secondary infection rate (SIR) among contacts, household infection rate, and predictors of transmission. We enrolled 87 households including 87 COVID-19 index cases (female 78.2%; median age: 47.0 years, IQR: 42.0-51.5) and 255 contacts (males: 52.9%; median age: 19.0 years, IQR: 11.0-43.5) consisting of their children (42%) or spouses/partners (28.2%). A total of 95/255 contacts were SARS-CoV-2 antibody positive leading to a SIR of 37.3% (95% confidence interval (CI): 31.3-43.5%). Viral transmission was observed in 54 households (62%). SARS-CoV-2 infection was asymptomatic in 33/95 (34.7%) of SARS-CoV-2-positive contacts. Independent predictors of virus transmission from index to contacts were housing surface area < 60 m 2 (OR: 5.6 [1.1; 28.2] and a four-member family compared to five (OR: 3.6 [1.2; 10.3]). Households represent a high-risk setting for SARS-CoV-2 transmission through close contact within the family amplified by the number of family members and the housing surface area., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: This study was performed during the early outbreak period of coronavirus disease 2019 (COVID-19) and the seasonal epidemics of other respiratory viral infections, in order to describe the extent of co-infections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with other respiratory viruses. It also compared the diagnostic performances of upper respiratory tract (URT) and lower respiratory tract (LRT) samples for SARS-CoV-2 infection., Methods: From 25 January to 29 March 2020, all URT and LRT samples collected from patients with suspected COVID-19 received in the virology laboratory of Pitié-Salpêtrière University Hospital (Paris, France) were simultaneously tested for SARS-CoV-2 and other respiratory viruses., Results: A total of 1423 consecutive patients were tested: 677 (47.6%) males, 746 (52.4%) females, median age 50 (range, 1-103) years. Twenty-one (1.5%) patients were positive for both SARS-CoV-2 and other respiratory viruses. The detection rate of SARS-CoV-2 was significantly higher in LRT than in URT (53.6% vs. 13.4%; p<0.0001). The analysis of paired samples from 117 (8.2%) patients showed that SARS-CoV-2 load was lower in URT than in LRT samples in 65% of cases., Conclusion: The detection of other respiratory viruses in patients during this epidemic period could not rule out SARS-CoV-2 co-infection. Furthermore, LRT samples increased the accuracy of diagnosis of COVID-19., (Copyright © 2020. Published by Elsevier Ltd.)