Temperature and humidity do not play any significant role in the spread of the novel coronavirus, a study published in the International Journal of Environmental Research and Public Health has claimed.
The study suggests that the transmission of the Covid-19 virus from one person to the next depends almost entirely on human behaviour, regardless of the weather conditions.
"The effect of weather is low and other features such as mobility have more impact than weather. In terms of relative importance, weather is one of the last parameters," said Dev Niyogi, a professor at the University of Texas (UT) at Austin, US, who led the research.
The study defined weather as "equivalent air temperature," which combines temperature and humidity into a single value. The scientists then analysed this value and tracked the coronavirus spread in different regions across the world from March to July 2020.
Researchers also investigated the relationship between the spread of coronavirus infection and human behaviour, using cell phone data to study travel habits. The study examined human behaviour in a general sense and did not attempt to connect it to how the weather may have influenced it.
The researchers compared weather with other factors using a statistical metric that breaks down the relative contribution of each factor towards a particular outcome. They found that the weather's relative importance at the county (in United States) level scale was less than 3 per cent, with no indication that a specific type of weather helped spread the virus more than another.
In contrast, the data showed the clear influence of human behaviour -- and the outsized influence of individual behaviours, researchers have claimed. Taking trips and spending time away from home were the top two contributing factors to the spread of Covid-19, with a relative importance of about 34 per cent and 26 per cent respectively, researchers added. They also noted that the next two important factors were population and urban density, with a relative importance of about 23 per cent and 13 per cent respectively.
"We shouldn't think of the problem as something driven by weather and climate. We should take personal precautions and be aware of the factors in urban exposure," said study co-author Sajad Jamshidi, a research assistant at Purdue University in the US.
Maryam Baniasad, a doctoral candidate at Ohio State University, said that assumptions about how coronavirus would respond with weather are largely informed by studies conducted in laboratory settings on related viruses. Baniasad said that this study illustrates the importance of studies that analyse how the coronavirus spreads through human communities. "When you study something in lab, it's a supervised environment. It's hard to scale up to society. This was our first motivation to do a more broad study," she added.