Even small breezes can increase virus transmission outdoors

In a recent study, researchers from the Indian Institute of Technology Bombay found that when someone coughs outside, "wind flowing in the same direction" can cause Covid-19 to replicate "faster over longer distances than in calm conditions." Co-author Amit Agrawal said, "The study is significant in that it points to the increased infection risk that coughing in the same direction as the wind could bring about."

The study, published in Physics of Fluids, showed that even a slight breeze of 5 miles per hour could make the virus more transmissible, and viral transmission grew with faster gusts of wind. This is because small whirlwinds allow large droplets to last longer in the air, so it takes longer for the viral load in the air to lessen.

"Based on the results, we recommend wearing masks outdoors, particularly in breezy conditions," Agrawal said. The researchers did not specify how large a gathering would need to be for viral transmission to be an issue, so wearing a mask, even with few people around, is still recommended.

"Other guidelines, such as coughing into an elbow or turning the face away while coughing, should also be followed," said a news release about the study.