D105-01 Impact of HVAC Systems on Detection of Respiratory Syncytial Virus, Influenza, and SARS-CoV-2 in Elementary School Classrooms

Abstract Introduction Adequate ventilation, often achieved with central heating, ventilation, and air conditioning (HVAC) systems, is necessary to reduce indoor viral transmission; however, the actual impact on viral detection within schools are unknown. In this study, we aim to assess the impact of central HVAC systems on the presence of SARS-CoV-2, influenza, and respiratory syncytial virus (RSV) within elementary classrooms. Methods As a part of the School Inner City Air Study (ClinicalTrials.gov NCT05953233), 177 vacuumed dust samples were collected monthly from March - June 2025 from all 45 classrooms across two schools within the same zip code in the Northeastern US - one with central HVAC and the other relying solely on windows and window air conditioning units for passive ventilation. Nucleic acid extraction was performed using the Maxwell HT Viral TNA Kit (Promega) on the Kingfisher Flex platform. Multiplexed real-time quantitative PCR was performed to simultaneously detect SARS-CoV-2, influenza A, influenza B, and RSV over 45 cycles of replication, with a cycle threshold 40 considered positive. Generalized linear mixed effect models were used to model the effect of central HVAC system on viral detection, adjusting for season, class dimensions (m3), and number of students per class, as well as random effects for classrooms and school. Results Viral detection was high across both schools, with overall prevalence rates of 78.5% for SARS-CoV-2, 48.6% for RSV, 7.3% for influenza A, and 17.5% for influenza B (Figure 1). Temporal trends in detection could be seen in all viruses across the study period. Presence of central HVAC system was not associated with a decreased likelihood of detection for SARS-CoV-2 (OR 2.40, 95% CI 0.73-7.94, p = 0.151), and RSV (2.15, 95% CI 0.84 - 5.55, p = 0.112), and was associated with increased likelihood of detection of Influenza A and B (OR 4.64, 95% CI 1.27-16.92, p = 0.020). Conclusions Despite sampling during the spring, detection of SARS-CoV-2, influenza and RSV in elementary schools remain high. Presence of central HVAC systems was not associated with reduced virus exposure in elementary classrooms. These findings underscore the need for further research on indoor air quality interventions to mitigate viral exposures in school environments. This abstract is funded by: National Institute of Health, American Lung Association