by ftl_ftw
Re: first question - yes, you can go into cities with plague cubes and put supplies there, to prevent more plague cubes for appearing.Note that after the prologue, at the start of a character's turn, if they're in a city with plague cubes, they'll have to scratch off an exposure. So plague cubes probably lead you to spend an action to leave a city after putting cubes down, but this is just a strategic choice which you can also choose to ignore.
Re: second question: yes, when an outbreak happens, it is possible for it to spread to the havens.