What reduces the risk of COVID-19 outbreaks from gatherings by 19 times?

Gatherings outside significantly reduce the risk of COVID-19 outbreaks compared to indoor gatherings due to a few critical factors. Outdoor settings typically allow for better air circulation and ventilation, which diminishes the concentration of virus particles in the air. This lower density of airborne virus reduces the likelihood of transmission during interactions. Additionally, outdoor gatherings often allow for more physical space between individuals, further decreasing the risk of close contact, which is a primary way the virus spreads.

While wearing masks, social distancing indoors, and limiting indoor gatherings can also mitigate risk significantly, they do not provide the same level of reduction in outbreak potential as outdoor gatherings do. The combination of natural ventilation and the ability to maintain greater physical distance contributes to the effectiveness of outdoor meetings in curbing the spread of COVID-19.