Cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management

Abstract

BackgroundThe Influenza A H1N1 virus can be transmitted via direct, indirect, and airborne route to non-infected subjects when an infected patient coughs, which expels a number of different sized droplets to the surrounding environment as an aerosol. The objective of the current study was to characterize the human cough aerosol pattern with the aim of developing a standard human cough bioaerosol model for Influenza Pandemic control.Method45 healthy non-smokers participated in the open bench study by giving their best effort cough. A laser diffraction system was used to obtain accurate, time-dependent, quantitative measurements of the size and number of droplets expelled by the cough aerosol.ResultsVoluntary coughs generated droplets ranging from 0.1 - 900 microns in size. Droplets of less than one-micron size represent 97% of the total number of measured droplets contained in the cough aerosol. Age, sex, weight, height and corporal mass have no statistically significant effect on the aerosol composition in terms of size and number of droplets.ConclusionsWe have developed a standard human cough aerosol model. We have quantitatively characterized the pattern, size, and number of droplets present in the most important mode of person-to-person transmission of IRD: the cough bioaerosol. Small size droplets (< 1 μm) predominated the total number of droplets expelled when coughing. The cough aerosol is the single source of direct, indirect and/or airborne transmission of respiratory infections like the Influenza A H1N1 virus.Study designOpen bench, Observational, Cough, Aerosol study

Violent expiratory events: on coughing and sneezing

“…Duguid 1946), with recent focus on the improvement of the precision of measurement of the small submicrometre range (e.g. Morawska 2006;Johnson et al 2011;Zayas et al 2012). An example of droplet size distribution for coughs is shown in figure 17, which indicates a peak drop size of ⇠15 µm, the associated settling speed being 6.5 mm s 1 in ambient air typical of winter indoor conditions.…”

Fluid dynamics of disease transmission

“…Within the airway system, sneezes and coughs consist of fast airflows interacting with relatively slow moving, thin fluid layers. The majority of the studies of drop size measurement (e.g., Zayas et al 2012;Yang et al 2007;Morawska et al 2009) focus on coughing, talking, or respiration. Turner et al (1941) used single flash photographs to record sneezes using a dark field imaging setup and highlighted parts of the complex nature of such emissions.…”

“…The droplet size spans the micrometer and millimeter scales, but no consensus on the size distribution can be found in the literature. The techniques for measuring expiratory droplet size distributions have included enumeration on glass slides (Duguid 1946), optical counting (Papineni and Rosenthal 1997), aerodynamic droplet sizing (Johnson et al 2011), interferometric Mie imaging (Morawska et al 2009), scanning mobility droplet sizing (Yang et al 2007), and laser diffraction (Zayas et al 2012). Despite these efforts, discrepancies persist between the reported size spectra.…”

Public health measures to combat airborne infections in hospitals

“…[5] Findings of a study has emphasized the need to adopt a multisectoral approach to ensure an optimal control on the droplets released by the patients. [7] In conclusion, acknowledging the global concern of airborne infections, hospital administrators should devise a comprehensive plan to minimize the potential areas of exposure of susceptible individuals to the respiratory symptomatic cases.…”