Tracking SARS-CoV-2 RNA in the air: Lessons from a COVID-19 outbreak in an infirmary unit

Abstract

Background: The duration and magnitude of SARS-CoV-2 air dispersal during nosocomial outbreaks remain uncertain. This study evaluates the impact of mobile modular high-efficiency particulate air filter units (MMHUs) on SARS-CoV-2 air dispersal.

Methods: We investigated a nosocomial COVID-19 outbreak in an infirmary unit. The viral load (VL) of SARS-CoV-2 in air samples was correlated with the VL in nasopharyngeal swabs with or without MMHU. These samples underwent whole-genome sequencing and phylogenetic analysis.

Results: Upon outbreak declaration (August 2, 2024, day 0), 44 (69.8%) of 63 patients acquired COVID-19 in Ward 2B (19 male) and 2C (25 female) by day 4. The VL of SARS-CoV-2 remained detectable in air until day 11 (2B) and day 20 (2C). The VL of air samples was significantly correlated with the VL in nasopharyngeal swabs collected on days 5, 7, 10, and 13 in 2C (r = -0.975, P = .004). Using MMHU, the mean daily ratio of SARS-CoV-2 RNA (copies/1,000 L of air/patient) in 2B was 5 times lower than in 2C from days 5 to 10. Whole-genome sequencing revealed all 41 tested strains belonged to the Omicron variant, KP.3.1.1, phylogenetically related to the prevailing community strains.

Conclusions: Using MMHU mitigates the duration and magnitude of SARS-CoV-2 air dispersal during nosocomial outbreak.

Keywords: Air dispersal; Air sampling; COVID-19; Outbreak.