Could summer sunlight inactivate coronavirus? Here’s what a new study says

A 34-minute dose of midday summertime sunlight can inactivate 90% or more of coronavirus, a recent study found.

Due to more intense ultraviolet light and radiation, the authors wrote COVID-19 “should be inactivated relatively fast during summer in many populous cities of the world,” and that sunlight will likely have a notable effect on the virus’ ability to spread.

The study, titled “Estimated Inactivation of Coronaviruses by Solar Radiation,” looked at how effective UVB rays had been at inactivating coronavirus at various locations around the world.

The authors found that a lack of sunlight, such as in the winter months, allows the coronavirus to survive and thrive even outdoors.

“In contrast, the virus will persist infectious for a day or more in winter (December-March), with risk of re-aerosolization and transmission in most of these cities,” the study said. Globally, most cities will face this seasonal challenge.

The new study also suggests that shelter-in-place orders and similar lockdown plans could be counterproductive for anyone sharing a roof with multiple people.

“Healthy people outdoors receiving sunlight could have been exposed to lower viral dose with more chances for mounting an efficient immune response,” it said.

While the effects of sunlight on other viruses have been studied for years, much less is known about the coronavirus, as its relative newness leaves a lot of unknowns, Cory Merow, co-author of “Seasonality and Uncertainty in COVID-19 Growth Rates,” told The New York Times.

Merow warns that social distancing and face masks are still necessary in the hotter months, as the virus can spread prolifically indoors and in close quarters.

“If everybody sits next to one another on the bus and coughs,” he said, “ultraviolet light is not going to protect you.”

Merow added that it’s unclear, based on his own research, if the summer heat and all it entails would slow the spread of coronavirus, he told the Times.

Another study, by MIT, casts doubt on the idea, saying it is “extremely unlikely that the spread of 2019-nCoV would slow down in the USA or Europe, due to environmental factors.”

In several states, including the Carolinas, Texas, Arizona and others, coronavirus cases are surging, McClatchy News reported.

Florida, the Sunshine State itself, is seeing record high case counts and hospitalizations due to COVID-19, according to the outlet. The state recently surpassed 100,000 total confirmed cases.

Health officials say community spread is largely to blame for the worsening situation.

“These are lower income people that, if they don’t work, they don’t eat,” Jackson Health CEO Carlos Migoya told McClatchy News. “Those people go out, they get infected, and then they bring it home and then they get the entire family infected.”

This story was originally published June 23, 2020 at 9:22 PM with the headline "Could summer sunlight inactivate coronavirus? Here’s what a new study says."