Short-range bioaerosol deposition and recovery of viable viruses and bacteria on surfaces from a cough and implications for respiratory disease transmission

Abstract

Knowledge of respiratory bacterium/virus distribution on surfaces is critical for studying disease transmission via the contact route. Here, we investigated the bioaerosol deposition and distribution on a surface from a cough experimentally. A cough generator was used to release bacterium/virus-laden droplets. A solid surface was placed in front of the cough generator at different relative distances (D ¼ 0.2, 0.5, 0.8, and 1.1 m) and angles (h¼30 , 60 , and 90). Benign bacteria and bacteriophages were used separately. Results showed that droplet jet directly impinged upon the surface and then spread out along the surface. The distributions of droplet volume and viable microorganisms along the surface were unimodal. We then identified the impaction region based on the droplet flow field from a particle imaging velocimetry technique, which corresponded with the peak position and high-volume area. The impaction region contained around 83% of droplet volume along the vertical axis of the surface. The peak position, peak value, and width of the impaction region were related to D and h. The microorganisms inside the droplets did not affect the droplet distribution on near surfaces. The front surface can work as a partition to block the cough jet and protect people behind, and can be smaller when it is installed closer to the coughing person. This work demonstrates a methodology to obtain distribution and viability of microorganism deposited on surface, and suggest guidelines to setting up a protective partition as a possible intervention method against disease transmission.

Respiratory bioaerosol deposition from a cough and recovery of viable viruses on nearby seats in a cabin environment

“…It was the same one used in our previous work. 28 The releasing velocity of cough droplets was around 12 m/s which is similar to the average cough droplet velocity of 11.7 m/s. The size distribution was similar to a real cough with the peak size of 10-20 µm.…”

“…After the deposition and sample collection, one part of the sample with size of 1 cm × 5 cm or 1 cm × 11 cm was cut for inspection using a microscope (Ni‐E, Nikon, Japan) to obtain the number concentration of deposited droplets. A microscopy method similar to our previous work was employed 28 . The droplets on pictures were automatically identified and counted by the software of the microscope.…”

Measurements of exhaled airflow velocity through human coughs using particle image velocimetry

“…Dudalski et al [ 36 ] measured the far-field human cough airflows from healthy and influenza-infected subjects, and obtained the time variation of peak velocity in the center of airflow jet but did not discuss the velocity distributions. Wang et al [ 37 ] measured the velocity using PIV and captured droplets on a solid surface that subjects faced when coughing. Although their frequency was very high (12,500 Hz), their research mainly focused on the distribution of droplets while not the airflow characteristics.…”

“…It is worth noting that Bourouiba et al [ 38 ] observed the trajectory of droplets from human sneezes with a very high-frequency PIV (up to 8000 Hz). Wang et al [ 35 ], and Wang et al [ 37 ] utilized a higher PIV (frequency >10,000) to measure the cough but did not explore the detailed velocity distribution.…”

Short-range bioaerosol deposition and inhalation of cough droplets and performance of personalized ventilation

“…coli was used to represent the bacterial pathogens inside cough droplets, while some infectious diseases are transmitted via virus laden aerosols. The study from Wang, Fu, and Chao (2020) found that bacteria or viruses inside cough droplets did not affect the short-range bioaerosol deposition and distribution on the front surfaces. Thus, it was expected that the results of this work based on bacterium E.coli could represent both the bacterium and virus laden droplet deposition on front person.…”