Well, I couldn't find a way to report any number of birds, it's not like it was dismissed because it was just one. And yes, I assumed it was the flu and that there was a system in place to report cases, so people more knowledgeable than I could decide what to do exactly (treat birds, track them, kill them, alert local farmers, something else or nothing). I couldn't find any traces of that system so I asked here, but apparently it just doesn't exist.
Also it seemed rather inappropriate to have a dying swan right next to a skate park full of kids.
Still not sure what to do if the resident family is infected. I guess nothing.