Hot or cold, weather alone doesn’t have a significant impact on...

The link between weather and COVID-19 is complicated. Weather affects the environment in which the coronavirus must survive before a new host is infected. But it also affects human behavior, which is how the virus is transmitted from one host to another.

The study, led by the University of Texas at Austin, provides clarity on the role of weather in COVID-19 infection. A new study found that temperature and humidity are not a major factor in the spread of the coronavirus.

That said, whether it’s hot or cold outside, the transmission of COVID-19 from one person to the next depends almost entirely on human behavior.

“The impact of weather is small and other traits like mobility have more of an impact than weather,” said Dev Niyogi, professor at UT Austin’s Jackson School of Geosciences and Cockrell School of Engineering who led the research. “In terms of relative importance, the weather is one of the last parameters.”

The research was published in the October 26th International journal of environmental research and public health.

Co-authors are Sajad Jamshidi, a research fellow at Purdue University, and Maryam Baniasad, a graduate student at Ohio State University.

In the study, weather was defined as the “equivalent air temperature” where temperature and humidity are combined into a single value. The scientists then analyzed how this value, tracked by coronavirus, spread in different areas from March to July 2020. They ranged in size from US states and counties to countries, regions, and around the world.

At the county and state levels, the researchers also looked at the relationship between coronavirus infection and human behavior, and used cell phone data to study travel habits.

The study looked at human behavior in general and made no attempt to link it to the influence of weather. On each scale, the researchers adjusted their analyzes so that the population differences did not distort the results.

Using scales, the scientists found that the weather had almost no influence. When compared to other factors using a statistical metric that breaks down the relative contribution of each factor to a given outcome, the relative importance of weather at the county level was less than 3% without any indication that any particular type of weather was causing the spread promoted over another.

In contrast, the data showed the clear influence of human behavior – and the oversized influence of individual behavior. Travel and time away from home were the top two drivers of COVID-19 growth, with relative importance of about 34% and 26% respectively. The next two important factors were population and urban density, with relative importance of about 23% and 13%, respectively.

“We shouldn’t see the problem as something that is determined by weather and climate,” said Jamshidi. “We should take personal precautions and be aware of factors of urban exposure.”

Baniasad, a biochemist and pharmacist, said assumptions about how the coronavirus would react with weather are largely supported by studies in laboratory settings of related viruses. She said this study illustrates the importance of studies analyzing how the coronavirus is spreading in human communities.

“When you study something in the laboratory, it’s a supervised environment. It’s difficult to scale to society, ”she said. “This was our first motivation to conduct a broader study.”

Marshall Shepherd, a professor of atmospheric science at the University of Georgia who was not involved in the study, said the research provides important insights into weather and coronavirus across scales.

“This important work highlights some of the allusions to weather-COVID-19 links and underscores the need to adequately address scientific challenges,” Shepherd said.

Niyogi said one of the key lessons learned from the coronavirus pandemic is the importance of analyzing phenomena on the “human level” – the scale on which people lead their daily lives. He said this research is an example of that kind of perspective.

“COVID it is claimed could change everything,” said Niyogi. “We looked at weather and climate outlooks as a system that we shrink, shrink, shrink and then see how it might affect humans. Now we’re going to flip the case and scale up, starting at the human exposure scale and then outward. This is a new paradigm that we will need to study virus exposure and human environmental modeling systems that incorporate new sensor and AI-like techniques. ”

The University of Texas at Austin, NASA, and the National Science Foundation funded the research.