Abstract
The dynamics and significance of aerosol transmission of respiratory viruses are still controversial, for the major reasons that virus aerosols are inefficiently collected by commonly used air samplers and that the collected viruses are inactivated by the collection method. Without knowledge of virus viability, infection risk analyses lack accuracy. This pilot study was performed to (i) determine whether infectious (viable) respiratory viruses in aerosols could be collected from air in a real world environment by the viable virus aerosol sampler (VIVAS), (ii) compare and contrast the efficacy of the standard bioaerosol sampler, the BioSampler, with that of the VIVAS for the collection of airborne viruses in a real world environment, and (iii) gain insights for the use of the VIVAS for respiratory virus sampling. The VIVAS operates via a water vapor condensation process to enlarge aerosolized virus particles to facilitate their capture. A variety of viable human respiratory viruses, including influenza A H1N1 and H3N2 viruses and influenza B viruses, were collected by the VIVAS located at least 2m from seated patients, during a late-onset 2016 influenza virus outbreak. Whereas the BioSampler when operated following our optimized parameters also collected virus aerosols, it was nevertheless overall less successful based on a lower frequency of virus isolation in most cases. This side-by-side comparison highlights some limitations of past studies based on impingement-based sampling, which may have generated false-negative results due to either poor collection efficiency and/or virus inactivation due to the collection process. IMPORTANCE The significance of virus aerosols in the natural transmission of respiratory diseases has been a contentious issue, primarily because it is difficult to collect or sample virus aerosols using currently available air sampling devices. We tested a new air sampler based on water vapor condensation for efficient sampling of viable airborne respiratory viruses in a student health care center as a model of a real world environment. The new sampler outperformed the industry standard device (the SKC BioSampler) in the collection of natural virus aerosols and in maintaining virus viability. These results using the VIVAS indicate that respiratory virus aerosols are more prevalent and potentially pose a greater inhalation biohazard than previously thought. The VIVAS thus appears to be a useful apparatus for microbiology air quality tests related to the detection of viable airborne viruses.
Highlights
IMPORTANCE The significance of virus aerosols in the natural transmission of respiratory diseases has been a contentious issue, primarily because it is difficult to collect or sample virus aerosols using currently available air sampling devices
Transmission of influenza viruses from one person to another can occur by three routes: direct contact of infectious secretions with mucus membranes of the upper respiratory tract (URT), contact of virus-containing large droplet sprays with surfaces of the URT, and inhalation of small aerosols and droplet nuclei that deposit in the lower respiratory tract (LRT) [1,2,3] A fourth route has been shown in animal models: ocular infection, wherein airborne influenza viruses come into contact with ocular surfaces [4]
Viable human respiratory viruses were recovered by the viable virus aerosol sampler (VIVAS) and the BioSampler in each of three separate air sampling intervals performed on 11 March, but no viruses were recovered in control runs performed with high-efficiency particulate air (HEPA)-filtered VIVAS and BioSampler air intakes
Summary
IMPORTANCE The significance of virus aerosols in the natural transmission of respiratory diseases has been a contentious issue, primarily because it is difficult to collect or sample virus aerosols using currently available air sampling devices. We tested a new air sampler based on water vapor condensation for efficient sampling of viable airborne respiratory viruses in a student health care center as a model of a real world environment. PCR methods, which have been widely used for virus quantification, provide a total count of the viral genomes (genome equivalents) but do not discriminate between genomes corresponding to viable versus nonviable viruses [13] These difficulties might account for the results of the study reported by Lindsley et al [14], wherein influenza virus RNA was detected in 14 of the 30 test subjects yet infectious virus was isolated from only 2 subjects. With the VIVAS as a tool, we investigated whether infectious respiratory virus aerosols could be collected from the air of a student infirmary during an influenza outbreak as a model of its potential use in a real world environment
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