The shape of social graphs is likely very different across countries, but I don’t know of studies checking this. However, there are anecdata aplenty. My hometown in Spain has a lot of part timers in senior living facilities, so you will find, for instance, physical therapists working 2 or 3 facilities over the course of a week. We have confirmed examples of one therapist who contracted the virus somewhere, and now it’s on every facility he visited: Over a hundred people tested positive with him as the only link.

There is also how common it is for adult children to live with their parents, who might be retired already. Different networks do seniors and millennials that go to different places and have different links, but help the infection travel fast.

Given the low ICU capacity, a single case like this can overwhelm a local hospital system, with predictable results.