Seasonal changes in UV could alter COVID emissions but not as much as social speed – ScienceDaily

Natural differences in ultraviolet radiation affect COVID-19 emissions, but the effect is relatively small compared to protective measures such as body speed, mask wear, and quarantine, according to a new study from Harvard University.

“Understanding the potential seasons in COVID-19 release could help inform our response to pandemic in the coming months,” said Jonathan Proctor, a graduate at the Harvard Data Science Initiative and the Harvard Environmental Center. ”These findings suggest that the frequency of COVID-19 may have a seasonal pattern, spreading faster in winter when it is darker than most. summer. “

Analyzing daily COVID-19 and weather data from more than 3,000 administrative departments in more than 170 countries, Proctor, along with co-authors Peter Huybers, also at Harvard University, Tamma Carleton and Kyle Meng from the University of California Santa Barbara and Jules Cornetet at the École Normale Supérieure Paris-Saclay of France found that COVID-19 transmission through population tended to be lower in the weeks following higher UV exposure. Results were published in the Proceedings of the National Academy of Sciences.

The term COVID-19 has been a mystery since the disease first appeared a year ago, although some have suggested that UV may play a role. Related species of coronaviruses such as SARS and MERS have been found to be sensitive to UV radiation and recent laboratory studies show that UV exerts the action of SARS-CoV-2, the virus that causes COVID-19, on the surface.

But efforts to understand the impact of UV in the real world have been limited by scarce data and the difficulty of separating climate variables from other emission drivers. To test for an environmental signal within the sound of the pandemic, the team compiled and cleaned up data from statistical organizations around the world. To avoid factors that may vary across sectors, such as health care infrastructure or population density, the team examined how referrals within a particular population changed according to changes in population. sunlight, temperature, rainfall and humidity that same population saw.

“We basically question whether daily changes in population conditions affect new COVID-19 cases up to two weeks later,” Meng explained.

The researchers studied the association between UV and COVID-19 using data from the onset of pandemic and then used that relationship to simulate how seasonal changes may affect transmission. COVID-19. They found that changes in UV between winter and summer led to a 7 percent reduction in the COVID-19 growth rate on average across the Northern Hemisphere, which is about half the average daily growth rate at the onset of the pandemic. Although this research shows that COVID-19 exhibits a seasonal pattern due to changes in UV, the overall seasonality of COVID-19 remains unclear due to uncertain effects from other environmental factors such as temperature and humidity.

“We’re confident about the UV effect, but this is just one piece of the full seasonal picture,” Carleton said.

The team noted that environmental impacts are just one of many factors determining the spread of COVID-19, and that the approximate effects of UV radiation in the Northern and Southern Hemispheres are a fraction of the magnitude of effects. previously evaluated anti-infection policies including quarantines and travel bans.

“As we saw in the U.S. last summer, UV exposure alone does not appear to stop the spread of the virus without strong social distance policies,” Proctor said. “Regardless of the weather, additional measures appear to be needed to significantly reduce the spread.”

The team analyzed the data in a number of ways and consistently found that the higher the UV, the lower the COVID-19 emissions, but it is not clear which method of control that effect. UV may destroy the virus on the surface or in aerosols, or people on sunny days may go out more where there is less movement. It is even possible that UV reduces the vulnerability to COVID-19 by stimulating vitamin D production and strengthening the immune system.

“There is still so much we don’t know about how environmental factors both directly and indirectly, although human behavior, affect the spread of the virus,” Huybers said. “However, a better understanding of the environmental impacts of COVID-19 may allow seasonal policies to change seasonally and may assist in informing vaccination strategies.