One Year Weekly Size-Resolved Air Sampling of SARS-CoV-2 in Hospital Corridors and Relations to the Indoor Environment

Background. Airborne SARS-CoV-2 plays a prominent role in COVID-19 transmission. Numerous studies have sampled air from patient rooms, but airborne spread to other hospital areas such as corridors is less investigated. Methods. Size-fractionated aerosol particles were collected weekly, with 12 hours of sampling time daily, in corridors at two infectious disease wards in southern Sweden between March 2020 and May 2021. Samples were analysed with real-time reverse transcription polymerase chain reaction (RT-qPCR) for detection of SARS-CoV-2 RNA. Indoor temperature, relative humidity, and CO₂ concentration were monitored during the sampling period. Results. 20 of the 784 collected samples contained SARS-CoV-2 RNA, although in low concentrations. Positive air samples were found in sizes between 0.14 and 8.1 μm, but none >8.1 μm. 45% were found in submicron particles. No clear seasonal pattern was observed among the positive samples. There was no significant difference in the positivity rate of the samples between the two wards. Conclusions. SARS-CoV-2 was only detected in 2.6% of the aerosol samples, which indicates that the spread of airborne virus from patient rooms to the corridor was limited.