Hefty caveats here that the study in question hasn’t yet been reviewed, BUT… National Review reports that Covid-19 *could* be much more likely to spread indoors than outdoors.
Chinese scientists identified 318 outbreaks with three or more cases, involving 1,245 confirmed cases.
They divided the venues in which the outbreaks occurred into six categories: homes, transport, food, entertainment, shopping, and miscellaneous. Many outbreaks involved more than one venue category.
Home outbreaks were the dominant category (254 of 318 outbreaks; 79.9%), followed by transport (108; 34.0%).
They identified only a single outbreak in an outdoor environment, which involved two cases.
They suggest that, “the transmission of respiratory infections such as SARS-CoV-2 from the infected to the susceptible is an indoor phenomenon.”