Pollen may help spread the novel coronavirus and other airborne germs, according to a study pub- lished in Physics of Fluids. Investi- gators noticed a connection between COVID-19 infection rates and pollen concen- trations on the National Allergy Map of the US. That led them to create a computer mod- el of all the pollen-producing parts of a willow tree. They then simulated outdoor gatherings of 10 or 100 people—some of them shedding COVID-19 particles—and exposed the “crowd” to 10,000 pollen grains from the tree. They used the temperature, wind speed, and humidity of a typical spring day in the US and found that the tree’s pollen passed through the crowd in less than 1 minute, which could significantly affect the virus load carried along with the pollen and increase the risk of infection. The investigators plan to learn more about the mechanisms behind the interaction between airborne pollen grains and the human respiratory system under different environmental conditions.