Respiratory virus RNA is detectable in airborne and droplet particles

Abstract

Aerosol transmission routes of respiratory viruses have been classified by the WHO on the basis of equilibrium particle size. Droplet transmission is associated with particles sized >5 µm in diameter and airborne transmission is associated with particles sized ≤5 µm in diameter. Current infection control measures for respiratory viruses are directed at preventing droplet transmission, although epidemiological evidence suggests concurrent airborne transmission also occurs. Understanding the size of particles carrying viruses can be used to inform infection control procedures and therefore reduce virus transmission. This study determined the size of particles carrying respiratory viral RNA produced on coughing and breathing by 12 adults and 41 children with symptomatic respiratory infections. A modified six-stage Andersen Sampler collected expelled particles. Each stage was washed to recover samples for viral RNA extraction. Influenza A and B, parainfluenza 1, 2 and 3, respiratory syncytial virus (RSV), human metapneumovirus and human rhinoviruses (hRV) were detected using RT-PCR. On breathing, 58% of participants produced large particles (>5 µm) containing viral RNA and 80% produced small particles (≤5 µm) carrying viral RNA. On coughing, 57% of participants produced large particles containing viral RNA and 82% produced small particles containing viral RNA. Forty five percent of participants produced samples positive for hRV viral RNA and 26% of participants produced samples positive for viral RNA from parainfluenza viruses. This study demonstrates that individuals with symptomatic respiratory viral infections produce both large and small particles carrying viral RNA on coughing and breathing.

Viability ofPseudomonas aeruginosain cough aerosols generated by persons with cystic fibrosis

“…Thus, we cannot comment on viable aerosol production during coughing by younger or healthier patients or in those with transient P aeruginosa infections. In addition, we used culture media that selected for aerobic gram-negative bacteria and we cannot provide data on other microbes, including Staphylococcus aureus, non-tuberculous mycobacteria or respiratory viruses 14 32 33. Future studies using other selective media to determine the viability of other microorganisms in cough aerosols are now required.…”

Influenza Virus Infectivity and Virulence following Ocular-Only Aerosol Inoculation of Ferrets

“…Small mammalian models (including mice, ferrets, rabbits, and cotton rats) have been established for the study of ocular inoculation of numerous respiratory viruses, including influenza virus, adenovirus, and RSV (1), but do not recapitulate potential ocular exposure to virus-containing aerosols expelled from infected individuals during breathing, coughing, or sneezing (20). Several mammalian models that utilize an aerosolized virus inoculum have been established to address this need but have been restricted to inhalation exposure (3).…”

Viable influenza A virus in airborne particles expelled during coughs versus exhalations

“…Influenza virus RNA has been detected in respirable airborne particles collected in healthcare facilities and other locations 9, 10, 11, 12, 13, 14, 15, 16. Influenza virus RNA also has been found in aerosol particles collected directly from infected patients while they were coughing and breathing 17, 18, 19, 20, 21, 22, 23. Six studies have demonstrated that influenza patients expel airborne particles containing viable virus 13, 18, 19, 21, 24, 25.…”