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Background A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak affecting 52 people from a large school community in Santiago, Chile, was identified (12 March) 9 days after the first case in the country. We assessed the magnitude of the outbreak and the role students and staff played using self-administered antibody detection tests and a self-administered survey. Methods The school was closed on 13 March, and the entire community was placed under quarantine. We implemented a home-delivery, self-administered, immunoglobin (Ig) G/IgM antibody test and survey to a classroom-stratified sample of students and all staff from 4–19 May. We aimed to determine the overall seroprevalence rates by age group, reported symptoms, and contact exposure, and to explore the dynamics of transmission. Results The antibody positivity rates were 9.9% (95% confidence interval [CI], 8.2–11.8) for 1009 students and 16.6% (95% CI, 12.1–21.9) for 235 staff. Among students, positivity was associated with a younger age (P  = .01), a lower grade level (P  = .05), prior real-time polymerase chain reaction (RT-PCR) positivity (P  = .03), and a history of contact with a confirmed case (P  < .001). Among staff, positivity was higher in teachers (P  = .01) and in those previously RT-PCR positive (P  < .001). Excluding RT-PCR–positive individuals, antibody positivity was associated with fever in adults and children (P  = .02 and P  = .002, respectively), abdominal pain in children (P  = .001), and chest pain in adults (P  = .02). Within antibody-positive individuals, 40% of students and 18% of staff reported no symptoms (P  = .01). Conclusions Teachers were more affected during the outbreak and younger children were at a higher risk for infection, likely because index case(s) were teachers and/or parents from the preschool. Self-administered antibody testing, supervised remotely, proved to be a suitable and rapid tool. Our study provides useful information for school reopenings. [ABSTRACT FROM AUTHOR]

Background. In Chile, the novel influenza A (H1N1) epidemic began in the middle-high income area of Santiago. Clinical and laboratory surveillance was intensified with the aim to characterize the epidemic and determine its impact in a large hospital setting. Methods. Demographic and clinical data were obtained from all patients whose symptoms met the clinical definition of influenza A (H1N1) infection during the epidemic period. Laboratory confirmation was obtained by use of a nasopharyngeal antigen detection test for influenza A and/or influenza A (H1N1) polymerase chain reaction (PCR). A case was considered confirmed if the antigen detection test result for influenza A and/or the PCR test result were positive. Results. The total number of emergency department (ED) visits increased by 88.5% from a mean of 14,489 ED visits in 2006-2008 to a mean of 27,308 ED visits in 2009, during the epidemic period. There were 10,048 patients who were clinically diagnosed with influenza A (H1N1), and they represented 78% of all visits, of which 4591 (45.6%) were laboratory confirmed. The median time from symptom onset to diagnosis was 1 day, and 99.7% of individuals received antiviral treatment. School-aged children represented 67% of ED visits at the beginning of the epidemic and 24% of ED visits at the end of the epidemic. Only 2% of cases were hospitalized; of these, 70% of cases occurred in patients 6-50 years of age, and 32% of cases occurred in patients who had an underlying medical condition. Eleven patients (age range, 1-53 years) required admission to the intensive care unit (ICU); 6 of these patients had pneumonia with or without hemodynamic shock. No influenza-associated deaths occurred. Conclusions. Many cases of influenza A (H1N1) occurred in school-aged and adult individuals who required an ED visit; these visits resulted in a low impact on the use of hospital beds. Aggressive ICU management and/or experience in extracorporeal membrane oxygenation significantly improved outcomes. Early antiviral treatment may have played an important role in the low number of severe cases. Vaccines targeted for school-aged children and young adults may modify the first epidemic wave in the northern hemisphere. [ABSTRACT FROM AUTHOR]