This is really interesting. Given lockdowns seem to be working, though, I think the takeaway is "the more people you can't avoid coming into contact with at home, the more important it is for no one to bring it into the house from elsewhere." https://champ.gothamist.com/champ/gothamist/news/data-shows-strong-link-between-rate-infection-and-how-many-people-live-you

Anyone with young kids in daycare knows they bring sh** home constantly to make you sick, for example. Increasing contact among the family coupled with less bringing sh** home can still reduce spread.

There might be stuff we can learn from how this correlation changed as distancing measures ramped up.

(A simple dumb way to think about it that keeps you from getting carried away with the implications of this: If it only spread within households and not between them, it .... couldn't spread.)

Random q I can't find on Google: is there a study on what % of the time a cold, flu, etc goes from spouse to spouse, child to parent etc? Just from experience I'm guessing it's very high even without being locked down together, so the difference might be marginal.

Again, thinking back to the kids' daycare days, getting them out of daycare put me in contact with them a lot more, but it stopped them from bringing stuff home every time a classmate had it, which sure seemed a lot bigger of an effect.