The evidence we have so far shows that the vast majority of cases are transmitted indoors: https://www.medrxiv.org/content/10.1101/2020.04.04.20053058v1 https:

The evidence we have so far shows that the vast majority of cases are transmitted indoors: https://www.medrxiv.org/content/10.1101/2020.04.04.20053058v1 https://www.medrxiv.org/content/10.1101/2020.04.04.20053058v... In practice, a transmission event happens through a certain amount of virus particles entering the body, and this doesn't seem to happen very often for Covid.