Wednesday 7 October 2020

Humidity levels could be key to coronavirus control

In terms of the climate, one research group maintain that as COVID-19 cases increase, understanding how climate affects the spread of the coronavirus is necessary. Aerosol of respiratory droplet transmission is well-known to be a primary vehicle for the rapid spread and continued circulation of viruses in humans. There is also strong support that environmental conditions will affect rates of virus transmission. With the SARS-CoV-2 virus, medical data has consistently detected the virus in the saliva of infected people. This is particularly so as winter virus infections are generally more common (and those of use based in the northern hemisphere) will experience cooler temperatures.

To this end, scientists have studied the impact of relative humidity, environmental temperature, and wind speed in relation to the human respiratory cloud and also with virus viability. 


 The key aspect from the research relates to a critical factor for the transmission of the infectious particles or virions (especially when they are immersed in respiratory clouds of saliva droplets).

This is the rate of evaporation. The importance of this is the way by which heat and mass transfer around and within respiratory droplets, affect the chance of infection, especially within a closed environment. The optimal conditions to reduce the chance of infection from coronavirus are environments with high temperature and low relative humidity. This is because such environs lead to high evaporation rates of saliva-contaminated droplets, and this is critical for reducing the virus viability.

The researchers call this factors the saliva liquid carrier-droplet evaporation rate. However, even under these optimal conditions the virus can still spread. This arises due to another factor: wind speed. This means the wind outdoors or air movement through air changes when indoors. Understanding the aerodynamics could influence social distancing guidelines. 

The significance of this research could be towards a better understanding of the evaporation and how this connects with climate effects. This could become the basis to a model that would enable scientists to better predict coronavirus concentration and hence to assess the viability of the virus or at least the potential for virus survival. Such a model could be possible through the use of a computational fluid dynamics platform. The researchers used a very specific model, called the three-dimensional multiphase Eulerian–Lagrangian computational fluid dynamics solver. This requires an understanding of the steady-state of heat and mass transfer in relation to flowing spherical particles, as viral particles 

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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