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Current Affairs

Droplet evaporation and spread of Covid-19

Date: 25 September 2020 Tags: Miscellaneous


A new study has now looked at evaporation of respiratory droplets — specifically those that contain virus, which help in spreading the infection.



The effect of temperature and humidity on the novel coronavirus has been studied a number of times since the pandemic took hold. So have the fluid dynamics and heat transfer aspects of the evaporation of droplets.



  • When temperature is high and relative humidity is low simultaneously, the study found a significant reduction in virus viability.

  • On the other hand, when RH is high, then the distance travelled by the droplet cloud, and the virus concentration remain significant — at any temperature.

  • This, the study notes, is in contradiction with what was previously believed by many epidemiologists.

  • The study cites the example of Delhi in July, when temperature and RH were both high, yet cases saw a surge.

  • The number of cases grew by more than half from 87,000 at the end of June to 1.35 lakh at the end of July, according to government records.

  • The researchers developed new theoretical correlations for the unsteady evaporation of coronavirus-contaminated saliva droplets.

  • It introduced the thermodynamic properties of virions (the complete virus) as a liquid. The research took into account humidity, temperature, and wind speed.

  • The key finding is that evaporation is a critical factor for the transmission of the infectious particles immersed in respiratory clouds of saliva droplets.