Aerosol SARS-CoV-2 in hospitals and long-term care homes during the COVID-19 pandemic.

Gary Mallach,Ryan Kulka,Tom Kovesi,Michaeline Mcguinty,Jay Krishnan,Anand Kumar,Bashour Yazji,Samantha B Kasloff,Benoit Robert,Todd Cutts,Sophia Den Otter-Moore,Amitava Mukherjee

doi:10.1371/journal.pone.0258151

Abstract

BackgroundFew studies have quantified aerosol concentrations of SARS-CoV-2 in hospitals and long-term care homes, and fewer still have examined samples for viability. This information is needed to clarify transmission risks beyond close contact.MethodsWe deployed particulate air samplers in rooms with COVID-19 positive patients in hospital ward and ICU rooms, rooms in long-term care homes experiencing outbreaks, and a correctional facility experiencing an outbreak. Samplers were placed between 2 and 3 meters from the patient. Aerosol (small liquid particles suspended in air) samples were collected onto gelatin filters by Ultrasonic Personal Air Samplers (UPAS) fitted with <2.5μm (micrometer) and <10 μm size-selective inlets operated for 16 hours (total 1.92m3), and with a Coriolis Biosampler over 10 minutes (total 1.5m3). Samples were assayed for viable SARS-CoV-2 virus and for the viral genome by multiplex PCR using the E and N protein target sequences. We validated the sampling methods by inoculating gelatin filters with viable vesicular stomatitis virus (VSV), and with three concentrations of viable SARS-CoV-2, operating personal samplers for 16hrs, and quantifying viable virus recovery by TCID50 assay.ResultsIn total, 138 samples were collected from 99 rooms. RNA samples were positive in 9.1% (6/66) of samples obtained with the UPAS 2.5μm samplers, 13.5% (7/52) with the UPAS 10μm samplers, and 10.0% (2/20) samples obtained with the Coriolis samplers. Culturable virus was not recovered in any samples. Viral RNA was detected in 15.1% of the rooms sampled. There was no significant difference in viral RNA recovery between the different room locations or samplers. Method development experiments indicated minimal loss of SARS-CoV-2 viability via the personal air sampler operation.

Highlights

Few studies have quantified aerosol concentrations of SARS-CoV-2 in hospitals and longterm care homes, and fewer still have examined samples for viability
Aerosol samples were collected onto gelatin filters by Ultrasonic Personal Air Samplers (UPAS) fitted with
RNA samples were positive in 9.1% (6/ 66) of samples obtained with the UPAS 2.5μm samplers, 13.5% (7/52) with the UPAS 10μm samplers, and 10.0% (2/20) samples obtained with the Coriolis samplers

Summary

Methods

We deployed particulate air samplers in rooms with COVID-19 positive patients in hospital ward and ICU rooms, rooms in long-term care homes experiencing outbreaks, and a correctional facility experiencing an outbreak. We validated the sampling methods by inoculating gelatin filters with viable vesicular stomatitis virus (VSV), and with three concentrations of viable SARS-CoV-2, operating personal samplers for 16hrs, and quantifying viable virus recovery by TCID50 assay. VeroE6 cells were seeded the day prior in 96-well plates to attain 80% confluence on the day of titrations [37]. Aerosol SARS-CoV-2 in hospitals and long-term care homes during the COVID-19 pandemic of fresh VCM prior to the addition of the sample inoculum. Samples being titrated for viable virus were 10-fold serially diluted in VCM with 50μL inoculum overlaid onto Vero E6 cells in replicates of 5 per dilution series. Plates were incubated at 37 ̊C +5% CO2 for 5–7 days and examined for CPE where virus titers were calculated via Reed-Muench procedure [37]

Results

Discussion

Conclusion