Are you a doctor? I’m not. I work in a hospital. I’ve worked in two others. This is what the experts tell me and my co workers because we have to clean and sanitize patient rooms. They tell us how germs spread.
I have studied environmental issues and chemical air pollution such as Ozone, smoke, Carbon Monoxide, as well as airborne germs get more concentrated in indoor environments, this is a safety issue for environmental concerns, not to mention the workers who go inside abandoned buildings or other enclosed environments where there are respiratory hazards of various kinds. I can attest that the doctors are right about contagion in indoor environments.