SARS-CoV-2 transmission with and without mask wearing or air cleaners in schools in Switzerland: A modeling study of epidemiological, environmental, and molecular data.

BACKGROUND: Growing evidence suggests an important contribution of airborne transmission to the overall spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), in particular via smaller particles called aerosols. However, the contribution of school children to SARS-CoV-2 transmission remains uncertain. The aim of this study was to assess transmission of airborne respiratory infections and the association with infection control measures in schools using a multiple-measurement approach. METHODS AND FINDINGS: We collected epidemiological (cases of Coronavirus Disease 2019 (COVID-19)), environmental (CO2, aerosol and particle concentrations), and molecular data (bioaerosol and saliva samples) over 7 weeks from January to March 2022 (Omicron wave) in 2 secondary schools (n = 90, average 18 students/classroom) in Switzerland. We analyzed changes in environmental and molecular characteristics between different study conditions (no intervention, mask wearing, air cleaners). Analyses of environmental changes were adjusted for different ventilation, the number of students in class, school and weekday effects. We modeled disease transmission using a semi-mechanistic Bayesian hierarchical model, adjusting for absent students and community transmission. Molecular analysis of saliva (21/262 positive) and airborne samples (10/130) detected SARS-CoV-2 throughout the study (weekly average viral concentration 0.6 copies/L) and occasionally other respiratory viruses. Overall daily average CO2 levels were 1,064 ± 232 ppm (± standard deviation). Daily average aerosol number concentrations without interventions were 177 ± 109 1/cm3 and decreased by 69% (95% CrI 42% to 86%) with mask mandates and 39% (95% CrI 4% to 69%) with air cleaners. Compared to no intervention, the transmission risk was lower with mask mandates (adjusted odds ratio 0.19, 95% CrI 0.09 to 0.38) and comparable with air cleaners (1.00, 95% CrI 0.15 to 6.51). Study limitations include possible confounding by period as the number of susceptible students declined over time. Furthermore, airborne detection of pathogens document exposure but not necessarily transmission. CONCLUSIONS: Molecular detection of airborne and human SARS-CoV-2 indicated sustained transmission in schools. Mask mandates were associated with greater reductions in aerosol concentrations than air cleaners and with lower transmission. Our multiple-measurement approach could be used to continuously monitor transmission risk of respiratory infections and the effectiveness of infection control measures in schools and other congregate settings.

Effects and utility of an online forward triage tool during the SARS-CoV-2 pandemic: a mixed method study and patient perspectives, Switzerland.

OBJECTIVE: To assess the effects (quantitatively) and the utility (qualitatively) of a COVID-19 online forward triage tool (OFTT) in a pandemic context. DESIGN: A mixed method sequential explanatory study was employed. Quantitative data of all OFTT users, between 2 March 2020 and 12 May 2020, were collected. Second, qualitative data were collected through key informant interviews (n=19) to explain the quantitative findings, explore tool utility, user experience and elicit recommendations. SETTING: The working group e-emergency medicine at the emergency department developed an OFTT, which was made available online. PARTICIPANTS: Participants included all users above the age of 18 that used the OFTT between 2 March 2020 and 12 May 2020. INTERVENTION: An OFTT that displayed the current test recommendations of the Federal Office of Public Health on whether someone needed testing for COVID-19 or not. No diagnosis was provided. RESULTS: In the study period, 6272 users consulted our OFTT; 40.2% (1626/4049) would have contacted a healthcare provider had the tool not existed. 560 participants consented to a follow-up survey and provided a valid email address. 31.4% (176/560) participants returned a complete follow-up questionnaire. 84.7% (149/176) followed the recommendations given. 41.5% (73/176) reported that their fear was allayed after using the tool. Qualitatively, seven overarching themes emerged namely (1) accessibility of tool, (2) user-friendliness of tool, (3) utility of tool as an information source, (4) utility of tool in allaying fear and anxiety, (5) utility of tool in medical decision-making (6) utility of tool in reducing the potential for onward transmissions and (7) utility of tool in reducing health system burden. CONCLUSION: Our findings demonstrated that a COVID-19 OFTT does not only reduce the health system burden but can also serve as an information source, reduce anxiety and fear, reduce potential for cross infections and facilitate medical decision-making.

Diagnostic accuracy of SARS-CoV-2 saliva antigen testing in a real-life clinical setting.

BACKGROUND: SARS-CoV-2 antigen tests with saliva facilitate examination in settings that lack trained personnel. However, little is known about the diagnostic accuracy in real-life clinical settings. Therefore, we studied the diagnostic accuracy of a saliva antigen test in diagnosing SARS-CoV-2 infection in a primary/secondary care testing facility. METHODS: Individuals who presented at a COVID-19 testing facility affiliated with a Swiss university hospital were prospectively recruited (n=377). Saliva specimen was obtained, and the PCL Inc. COVID19 Gold antigen test was conducted in parallel with 2 real-time polymerase chain reaction (RT-PCR) assays from a nasopharyngeal swab. RESULTS: RT-PCR results were positive in 53 individuals, corresponding to a prevalence of 14.1% (missing material in 1 individual). The PCL saliva antigen test was positive in 22 individuals (5.8%) and negative in 354 (93.9%). The sensitivity of the saliva antigen test was 30.2% (95% confidence interval 18.3, 44.3), both overall and in symptomatic individuals. The specificity was 98.1% (96.0, 99.3). CONCLUSIONS: The diagnostic accuracy of a SARS-CoV-2 saliva antigen test in a primary/secondary care testing facility was remarkably lower than that reported in the manufacturer's specifications.

The effect of the COVID-19 pandemic on the epidemiology of positive blood cultures in Swiss intensive care units: a nationwide surveillance study.

BACKGROUND: Evidence about the impact of the pandemic of COVID-19 on the incidence rates of blood cultures contaminations and bloodstream infections in intensive care units (ICUs) remains scant. The objective of this study was to investigate the nationwide epidemiology of positive blood cultures drawn in ICUs during the first two pandemic waves of COVID-19 in Switzerland. METHODS: We analyzed data on positive blood cultures among ICU patients, prospectively collected through a nationwide surveillance system (ANRESIS), from March 30, 2020, to May 31, 2021, a 14-month timeframe that included a first wave of COVID-19, which affected the French and Italian-speaking regions, an interim period (summer 2020) and a second wave that affected the entire country. We used the number of ICU patient-days provided by the Swiss Federal Office of Public Health as denominator to calculate incidence rates of blood culture contaminations and bloodstream infections (ICU-BSI). Incidence rate ratios comparing the interim period with the second wave were determined by segmented Poisson regression models. RESULTS: A total of 1099 blood culture contaminations and 1616 ICU-BSIs were identified in 52 ICUs during the study. Overall, more episodes of blood culture contaminations and ICU-BSI were observed during the pandemic waves, compared to the interim period. The proportions of blood culture contaminations and ICU-BSI were positively associated with the ICU occupancy rate, which was higher during the COVID-19 waves. During the more representative second wave (versus interim period), we observed an increased incidence of blood culture contaminations (IRR 1.57, 95% CI 1.16-2.12) and ICU-BSI (IRR 1.20, 95% CI 1.03-1.39). CONCLUSIONS: An increase in blood culture contaminations and ICU-BSIs was observed during the second COVID-19 pandemic wave, especially in months when the ICU burden of COVID-19 patients was high.

Diagnostic accuracy of a SARS-CoV-2 rapid antigen test in real-life clinical settings.

BACKGROUND: Laboratory tests are a mainstay in managing the COVID-19 pandemic, and high hopes are placed on rapid antigen tests. However, the accuracy of rapid antigen tests in real-life clinical settings is unclear because adequately designed diagnostic accuracy studies are essentially lacking. OBJECTIVES: The aim of this study was to assess the accuracy of a rapid antigen test in diagnosing SARS-CoV-2 infection in a primary/secondary care testing facility. METHODS: Consecutive individuals presenting at a COVID-19 testing facility affiliated to a Swiss University Hospital were recruited (n = 1465%). Nasopharyngeal swabs were obtained, and the Roche/SD Biosensor rapid antigen test was conducted in parallel with two real-time PCR tests (reference standard). RESULTS: Among the 1465 patients recruited, RT-PCR was positive in 141 individuals, corresponding to a prevalence of 9.6%. The Roche/SD Biosensor rapid antigen test was positive in 94 patients (6.4%), and negative in 1368 individuals (93.4%; insufficient sample material in 3 patients). The overall sensitivity of the rapid antigen test was 65.3% (95% confidence interval [CI] 56.8-73.1), the specificity was 99.9% (95% CI 99.5-100.0). In asymptomatic individuals, the sensitivity was 44.0% (95% CI 24.4-65.1). CONCLUSIONS: The accuracy of the SARS-CoV-2 Roche/SD Biosensor rapid antigen test in diagnosing SARS-CoV-2 infections in a primary/secondary care testing facility was considerably lower compared with the manufacturer's data. Widespread application in such a setting might lead to a considerable number of individuals falsely classified as SARS-CoV-2 negative.