A Japanese study of 100 cases found that the odds of catching the coronavirus are nearly 20 times higher indoors than outdoors. Outdoor gatherings lower risk because wind disperses viral droplets, and sunlight can kill some of the virus. Open spaces prevent the virus from building up in concentrated amounts and being inhaled, which can happen indoors when infected people exhale in a confined space for long stretches of time, said Dr. Julian W. Tang, a virologist at the University of Leicester. [source NYT]