“SARS-CoV-2 airborne detection within different departments of a COVID-19 hospital building and evaluation of air cleaners in air viral load reduction”

The pandemic of COVID-19 has brought in light the necessity for the development of novel detection methods for airborne transmitted pathogens, and the importance of effective clean air measures in hospital departments. In this study, airborne SARS-CoV-2 and particle matter (PM1, PM2.5) detection was performed in different areas of the COVID-19 building at the Ippokrateio University Hospital in Thessaloniki, Greece. More specifically, Sioutas cascade impactors were placed in the ICU (Intensive Care Unit) and HDU (High-Dependency Unit) on the first floor, and at the corridor and rooms at the COVID-19 clinic on the second floor. Furthermore, TECORA air pumps were placed at the building entrance to measure for PM1 and PM2.5. Afterwards, in a COVID room with confirmed air viral load an air cleaner was placed to examine the effect on viral load reduction. Results showed that no viral copies were detected in the air of ICU and HDU departments, in which negative pressure air filtration with HEPA filters is applied. On the contrary, viral load was effectively detected in rooms and corridors of the COVID floor and ranged from 25,9 to 1123,7 copies/m 3 . PM1 filters showed 77.8 % viral positivity, and PM2.5 filters were 38.5 % virus positive. Moreover, air viral load in the COVID room with an air cleaner showed a reduction of up to 98.1 %. In conclusion, SARS-CoV-2 was effectively detected in the air of different areas in the COVID building after continuous sampling ranging between 24 h and 7 days, and it was shown how important and effective air cleaners are as first-line measures against pathogen airborne transmission in hospital environments. • Significant differences were found in air viral load between COVID clinic areas. • No virus has been detected in the air of ICU and HDU hospital units. • Air viral load in COVID clinic ranged from 25,9 to 1123,7 copies/m 3 . • No correlation between PM1 and PM2.5, and SARS-CoV-2 burden. • Air cleaner showed an effective reduction of air viral load, reaching 98.1 %.