ABSTRACT
Background: There is increasing evidence for aerosol-based transmission of SARS-CoV-2, with particulate matter (PM) a possible vector. Air surveillance is necessary to safeguard public spaces. Aim(s): To characterise SARS-CoV-2 distribution in aerosols collected in hospital and public spaces and determine best sampling methods for surveillance. Method(s): Over 8 months in 2021, 8 samplers collected liquid bioaerosols and size-fractioned particulate matter(PM) in hospitals (ICU, Respiratory ward and communal waiting areas), a London railway and underground station, a university, and a primary school. RNA was extracted from samples and RT-qPCR targeting the N-gene of SARSCoV-2 was performed. Samples were cultured on Vero cells. Result(s): 209 air samples were obtained with 20 positive for SARS-CoV-2. 15 positive samples were from hospitals, 10 from outpatient waiting areas (ED waiting area, Chemotherapy Day Unit), 2 of which had the B.1.1.7 mutation (alphavariant) on sequencing, and 5 positive samples from rooms housing SARS-CoV-2 positive patients on ICU and respiratory wards. 5 positive samples were obtained via a portable sampler on two separate journeys in a London underground carriage. SARS-CoV-2 was detected mostly in PM samplers (n=17) compared to liquid bioaerosol samplers (positive sample pick-up 13% vs 4%respectively), in fine particles <=2.5mum(PM2.5) in diameter (n=14). No samples were cultured on Vero cells. Conclusion(s): Size-fractioned particulate matter samplers may be more efficient than liquid bioaerosol samplers in detecting and monitoring SARS-CoV-2 in the air. SARS-CoV-2 is most detected on fine particles, giving support to PM2.5 acting as a vector for aerosol-based transmission.
ABSTRACT
The presence of SARS-CoV-2 in untreated sewage has been confirmed in many countries but its incidence and infection risk in contaminated waters is poorly understood. The River Thames in the UK receives untreated sewage from 57 Combined Sewer Overflows (CSOs), with many discharging dozens of times per year. This study investigated if such discharges provide a pathway for environmental transmission of SARS-CoV-2. Samples of wastewater, surface water, and sediment collected close to six CSOs on the River Thames were assayed over eight months for SARS-CoV-2 RNA and infectious virus. Bivalves were also sampled as an indicator species of viral bioaccumulation. Sediment and water samples from the Danube and Sava rivers in Serbia, where raw sewage is also discharged in high volumes, were assayed as a positive control. No evidence of SARS-CoV-2 RNA or infectious virus was found in UK samples, in contrast to RNA positive samples from Serbia. Furthermore, this study shows that infectious SARS-CoV-2 inoculum is stable in Thames water and sediment for <3 days, while SARS-CoV-2 RNA is detectable for at least seven days. This indicates that dilution of wastewater likely limits environmental transmission, and that detection of viral RNA alone is not an indication of pathogen spillover.