2scents, Syag – prolonged contact seems to be more dangerous.
A simple explanation, not sure whether it captures the whole phenomenon: a person gets initial load, immune system starts reacting. Now, it is a race – virus propagating deeper and doing it’s job or immunity building up. So, the more initial load is, the more chances that the virus will win over immunity. There are a lot of secondary indicators of this: cases at home; increase in cases in US South during summer (AC, less outdoors) and in the North during winter (heat, less outdoors).
Other than that, may depend on the lifestyle. I presume that the kids spend most of the day at school, adults at work and in shul and beis midrash. If someone spends the day in the airport, talking to passerbys in the mall, in medical offices, then, of course, they are at risk there also.
But I presume that airports and malls do HVAC and most responsible medical offices (most of our doctors sent us email about that months ago). I helped a couple of mosdos on this, but don’t know what the overall picture is.