Quantification of airborne respiratory microflora provides insights into airborne infection risk

Abstract

Objective: To develop airborne respiratory microflora quantification as a method of quantifying airborne infection risk that is more readily applicable than airborne pathogen sampling, without being subject to the limitations and caveats of CO2 monitoring.

Methods: Digital PCR targeting a mixture of Streptococcus and Haemophilus genera common to the respiratory tract was first tested under laboratory conditions and then tested on aerosol sampled from around a hospital in Sydney, with PCR quantification of SARS-CoV-2 genome copies also being carried out on the samples.

Results: Clear signals were obtained from every location within the hospital, with a significantly higher signal being observed in more densely crowded, less well-ventilated areas. When SARS-CoV-2 was present within the aerosol samples, the respiratory microflora signal correlated with the number of SARS-CoV-2 copies.

Conclusions: Airborne respiratory microflora can be used as a marker for airborne infection risk. Using the value in conjunction with pathogen sampling provides in-depth insights into the relative infection risk of a space, as well as a clear marker which can be used to compare between different pathogen sampling studies.

Keywords: Aerobiology; Disease transmission; Infection risk quantification; SARS-CoV-2.