Evaporation critical to coronavirus transmission as weather changes
Impact of evaporation on virus survival, concentration, transmission


Date:
September 22, 2020
Source:
American Institute of Physics
Summary:
As COVID-19 cases continue to rise, it is increasingly urgent
to understand how climate impacts the spread of the coronavirus,
particularly as winter virus infections are more common and the
northern hemisphere will soon see cooler temperatures. Researchers
studied the effects of relative humidity, environmental temperature,
and wind speed on the respiratory cloud and virus viability. They
found a critical factor for the transmission of the infectious
particles is evaporation.



FULL STORY ==========================================================================
As COVID-19 cases continue to rise worldwide, it is increasingly urgent to understand how climate impacts the continued spread of the coronavirus, particularly as winter virus infections are more common and countries
in the northern hemisphere will soon see cooler temperatures.


==========================================================================
In a paper in Physics of Fluids, by AIP Publishing, researchers studied
the effects of relative humidity, environmental temperature, and wind
speed on the respiratory cloud and virus viability. They found that a
critical factor for the transmission of the infectious particles, which
are immersed in respiratory clouds of saliva droplets, is evaporation.

"Suppose we have a better understanding of the evaporation and its
relation to climate effects. In that case, we can more accurately
predict the virus concentration and better determine its viability or the potential for virus survival," said Dimitris Drikakis, one of the authors.

Despite the importance of airborne droplet transmission, research
regarding heat and mass transfer around and within respiratory droplets containing the virus has been scarce.

To address the challenge, the researchers developed theoretical
correlations for the unsteady evaporation of coronavirus-contaminated
saliva droplets. They implemented the theory in an advanced computational
fluid dynamics platform and studied the effects of weather conditions
on airborne virus transmission.

"We found high temperature and low relative humidity lead to high
evaporation rates of saliva-contaminated droplets, thus significantly
reducing the virus viability," said co-author Talib Dbouk.

Additionally, the researchers observed the travel distance and
concentration of the droplet cloud continued to be significant, even
at high temperatures if the relative humidity is high. The wind speed
is another crucial factor that might alter all the rules for the social distancing guidelines.

These findings help explain why the pandemic increased during July
in different crowded cities around the world, such as Delhi, which
experienced both high temperatures and high relative humidity. It
also provides a crucial alert for the possibility of a second wave
of the pandemic in the coming autumn and winter seasons, where low
temperatures and high wind speeds will increase airborne virus survival
and transmission.

This study adds to the growing body of research that reinforces the
importance of social distancing and the use of face masks to prevent
full virus spread.

The results reveal the importance of weather conditions in the virus's viability, which can help guide the design of measures in both indoor and outdoor environments, to reduce airborne virus transmission in private
and public spaces.


========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Talib Dbouk, Dimitris Drikakis. Weather impact on airborne
coronavirus
survival. Physics of Fluids, 2020; 32 (9): 093312 DOI:
10.1063/5.0024272 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200922112304.htm

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