Indoor air sampling strategies by active bioaerosol samplers: a case study to detect SARS-CoV-2 in hospital settings

This study demonstrates the applicability of air sampling for the detection of SARS-CoV-2 in a hospital by means of active bioaerosol samplers following a specifically designed air sampling strategy based on digital mapping of the architectural layout of the ward to minimize disruptions of health care activities and reducing operator risks. Prior to the experimental study, some model tests were conducted using the air sampler with a tunable flow rate to determine the most suitable real time polymerase chain reaction (RT-PCR) based detection method. Preliminary results showed the need to perform intensive extraction protocols combined with Real-time reverse transcription PCR (rRT-PCR), rather than conventional, to enhance sensitivity. The experimental study was conducted within the general medicine ward of Spedali Civili Hospital in Brescia during the winter of 2021/2022, a period marked by a high prevalence of COVID-19 cases using three active air sampling devices: Coriolis Compact, Coriolis Micro®, and BioSpot GEM®. Environmental parameters, such as room size, occupancy, ventilation rates, and activities performed during sampling, and patients’ conditions were documented to contextualize the findings. The virus was detected in a few rooms with concentrations ranging from 1171 to 2225 copies/m 3 . These findings support the integration of routinary air sampling as tools for control and assessment of transmission risks, not only for SARS-CoV-2 but generalized to all airborne pathogens, supporting patient management and infection control in health care settings. • Air sampling of SARS-CoV-2 was tested in an operational hospital ward. • Three air samplers were compared under real clinical conditions. • Viral RNA was detected only after pre-concentration of high-volume samples. • 3D mapping supported efficient sampling with minimal disruption to the ward. • Results support air sampling as a tool for infection control and surveillance.