关键词： SARS-CoV-2   Epidemiology survey   Masks   Social distancing   Risk factors   Tropics   SARS-COV-2   RISK  

摘要： Background: In July 2021, amid occasional COVID-19 community transmission, an outbreak in a seafood wholesale centre propagated secondary clusters in sheltered markets in Singapore. This period offers a unique chance to study COVID-19 transmission risk factors related to environmental features and personal behaviours in markets. Only 40 % of the population was vaccinated during this period. Methods: A two-tier case-control study was conducted. The first tier entailed site assessments of markets where primary cases, presumed to have acquired COVID-19 at the seafood wholesale centre, worked. Markets with secondary cases (case markets) were compared against those without (control markets). The second tier comprised telephone questionnaires administered to individuals who worked at or visited the three markets with the highest number of secondary cases, with respondents either testing positive or negative for SARS-CoV-2. Results: Assessment of 38 markets showed that markets "seeded" with more primary cases were more likely to experience a secondary outbreak (adjusted odds ratio, aOR: 2.0; 95% confidence interval, CI: 1.3-4.7). From 333 visitor responses, maintaining social distancing (aOR: 0.34; 95 % CI: 0.11-1.06) and completing vaccination (aOR: 0.25; 95 % CI: 0.07-0.95) decreased infection risk, while using public washrooms increased the risk (aOR: 3.12; 95% CI: 0.87-11.00). Among 86 staff responses, statistically significant risk factors were gender and mask type: male staff (aOR: 0.14; 95 % CI: 0.02-0.62) and those wearing surgical/N95 masks (aOR: 0.10; 95 % CI: 0.01-0.71) had lower infection risk. Wider aisles of the markets correlated with a higher chance of secondary transmission (aOR: 2.5; 95 % CI: 1.3-6.7). Conclusion: These findings underscore the importance of considering both built environment features and individual behaviours in devising effective measures to mitigate COVID-19 transmission in markets and community hubs in general. The observed association

关键词： Myocarditis   COVID-19 vaccine-associated myocarditis   Cardiac MRI   Myocardial injury   LGE late gadolinium enhancement   MIS-C multisystem inflammatory syndrome in children  

摘要： Background We aimed to study the clinical characteristics, myocardial injury, and longitudinal outcomes of COVID-19 vaccine-associated myocarditis (C-VAM). Methods In this longitudinal retrospective observational cohort multicenter study across 38 hospitals in the United States, 333 patients with C-VAM were compared with 100 patients with multisystem inflammatory syndrome in children (MIS-C). We included patients ≤30 years of age with a clinical diagnosis of acute myocarditis after COVID-19 vaccination based on clinical presentation, abnormal biomarkers and/or cardiovascular imaging findings. Demographics, past medical history, hospital course, biochemistry results, cardiovascular imaging, and follow-up information from April 2021 to November 2022 were collected. The primary outcome was presence of myocardial injury as evidenced by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging. Findings Patients with C-VAM were predominantly white (67%) adolescent males (91%, 15.7 ± 2.8 years). Their initial clinical course was more likely to be mild (80% vs. 23%, p < 0.001) and cardiac dysfunction was less common (17% vs. 68%, p < 0.0001), compared to MIS-C. In contrast, LGE on CMR was more prevalent in C-VAM (82% vs. 16%, p < 0.001). The probability of LGE was higher in males (OR 3.28 [95% CI: 0.99, 10.6, p = 0.052]), in older patients (>15 years, OR 2.74 [95% CI: 1.28, 5.83, p = 0.009]) and when C-VAM occurred after the first or second dose as compared to the third dose of mRNA vaccine. Mid-term clinical outcomes of C-VAM at a median follow-up of 178 days (IQR 114–285 days) were reassuring. No cardiac deaths or heart transplantations were reported until the time of submission of this report. LGE persisted in 60% of the patients at follow up. Interpretation Myocardial injury at initial presentation and its persistence at follow up, despite a mild initial course and favorable mid-term clinical outcome, warrants continued clinical surveillance and lon