Increase in COVID-19 spread linked to natural UV level decrease: Study

Natural variations in ultraviolet riation influences spre of vel Coronavirus says a new study which ds that effect is still modest compared to that of measures like physical distancing, and mask-wearing.

findings, published in journal PNAS, suggests that incidence of COVID-19 may have a seasonal pattern in which virus spres faster in winter when it's darker with lower levels of UV riation than during summer.

"Understanding potential seasonality of COVID-19 transmission could help inform our response to pandemic in coming months," said Jonathan Proctor, a co-author of study from Harvard University in US.

In research, scientists analysed daily COVID-19 and wear data from over 3,000 ministrative regions in more than 170 countries.

y found that spre of COVID-19 through a population tended to be lower in weeks following higher UV exposure.

While reasons for seasonal variations in spre of COVID-19 remain a mystery, researchers said re have been some clues that UV could play a role.

y said related species of coronaviruses such as SARS and MERS were found to be sensitive to UV riation with recent laboratory studies showing that UV inactivates SARS-CoV-2, virus that causes COVID-19, on surfaces.

But scientists ded that attempts to understand influence of UV in real world have been limited by scarce data and difficulty of isolating climate variables from or factors driving spre of virus.

So scientists compiled and cleaned data from statistical ncies around world and examined how transmission within a particular population changed according to variations in sunlight, temperature, rainfall, and humidity.

"We basically ask wher daily fluctuations in environmental conditions experienced by a population affect new COVID-19 cases up to two weeks later," explained study co-author Kyle Meng from University of California Santa Barbara in US.

scientists evaluated relationship between UV and COVID-19 using data from beginning of pandemic and n used that relationship to simulate how seasonal changes might influence spre of coronavirus.

y found that changes in UV between winter and summer led to a 7-percent point decrease in COVID-19 growth rate on aver across rrn Hemisphere.

According to researchers, this is about half aver daily growth rate at beginning of pandemic.

While findings of current study show that COVID-19 exhibits a seasonal pattern due to changes in UV, scientists said full seasonality of COVID-19 still remains unclear.

y explained that this is due to uncertain influences of or environmental factors such as temperature and humidity.

"We are confident of UV effect, but this is only one piece of full seasonality picture," said Jules Cornetet, ar co-author of study.

However, scientists cautioned that UV exposure alone is unlikely to stop spre of virus without strong social distancing policies.

"Regardless of wear, ditional measures appear to be necessary to substantially slow spre," Proctor said.

researchers ded that it is also unclear what mechanism is driving this effect.