Dispersion of Cough Droplets

Angie SzumlinskiStudies

The severe acute respiratory syndrome coronavirus SARS-CoV-2 pandemic has spread worldwide progressively since it was first identified in Wuhan, China in December 2019. Although the transmission mechanism of SARS-CoV-2 remains unclear, it is generally agreed that the airborne transmission route cannot be dismissed. In yet another study, the fluid flow and droplet dispersion from respiratory events, such as a cough, in a tropical, outdoor environment were evaluated. The effects of relative humidity, wind speed, and social distancing on the droplet dispersion were investigated. Here are the highlights and recommendations from the study:

  1. Droplets less than 50 µm in diameter can remain airborne over long distances and the travel distances for large droplets cannot be underestimated.
  2. The presence of non-volatile components generally reduces the evaporation rate of droplets. For large droplets, shrinkage due to evaporation results in an increase in lifetime and travel distance.
  3. Large droplets may travel more than 1 µm under windless conditions. The travel distance correlates well with the wind speed.
  4. Social distancing is generally effective at reducing the droplet volume as well as the viral load deposited on the listener. The viral load could increase significantly, however, through successive coughs or higher viral loads.
  5. Droplet deposition on skin and clothes may not directly lead to infection however secondary transmission modes, including face, mouth, or nose touching need to be avoided. Hygiene measures such as washing hands and exposed surfaces are highly recommended.
  6. Young children may be at greater risk compared to adults based on the typical downward cough trajectory. Surgical masks are known to be effective at trapping large droplets and therefore are recommended.

There is much more scientific information in the study and it’s worth the read. In a nutshell, this study affirms pretty much what we have known, and it is nice to have something to read that agrees with the research we are trusting today!

Stay strong, stay the course, stay well, mask up, and stay tuned!