"Mysterious respiration problems, fever and other alarming symptoms arised after a simple bath in the sea. A bad sunday for tens of bathers in Genova, checked into hospital after feeling sick on the beach." (from il corriere)
Welcome to the sunny country. They suggest it's an alga. Could be. What kind of alga can be so harmful anyway?
Well, I don't care. I would never swim in the sea in front of Genova. You must be crazy or desperate to do that. Which, btw, most of our italian workers-on-holiday are.
You came to this blog for some advice on your next vacation in Italy?
Don't come in August, don't bathe near cities or even villages, don't mingle with desperate Italians on vacation. They're crazy.

* * update: the people on the beach got actually intoxicated by an alga. It's a tropical alga that lives now in the Mediterranean thanks to the higher temperatures. It was blossoming. So don't come to Italy at all. Here burning alga flowers floating can send you to hospital.