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Current Affairs

Seasonal UV radiation and Covid-19 trends

Date: 25 December 2020 Tags: miscellaneous


New research has looked at the influence of ultraviolet radiation from the Sun and found evidence that higher natural UV radiation reduces Covid-19 transmission.



The effect of seasonal factors such as temperature and humidity on covid-19 infection remains yet to be fully understood. 



  • The researchers stress that seasonal changes in UV are just one of many causes of change in Covid-19 case rates. The influence of UV is modest compared to policy measures such as travel restrictions, school closures, or event cancellations. 

  • Other research has looked at how artificial UV light can inactivate the coronavirus, it is also important to note that this is not the same as the effect of the sun’s UV radiation.

  • UV disinfectants currently in use today rely on wavelengths in a range called UV-C. Such wavelengths do not reach us naturally from the Sun, as these are absorbed by the ozone layer. 

  • In sunlight that reaches the Earth, the wavelengths are in the range known as UV-A (and to an extent in the range UV-B).

  • The study compared various populations to themselves over time, and tested whether daily variations in UV radiation lead to changes in Covid-19 cases up to three weeks in the future.

  • Based on changes in UV, the model predicted Covid-19 growth rates for the temperate zones north and south of the tropics.


  • Between January and June, Covid-19 growth rates would increase by 7.3 percentage points in southern temperate locations and decline by 7.4 percentage points in the northern temperate ones.

  • When the seasons flip, growth rates in December compared with July were predicted to decrease by 7.7 percentage points in southern temperate regions, and jump by 7.8 percentage points in northern areas.

  • However the development is not wholly attributed to UV radiation but to other factors such as population density, climate, social habits, national regulations etc.