Actually, some doctor/scientist dude said this afternoon (sorry was supposed to be working so didn't get a name) said what they had died of was an organism that's always present in river/lake water. In the summer it multiplies, so more deaths are caused by it. He explained the elderly and very young who's immune systems are weak are usually the ones who can't fight it. The deaths reported in LA were elderly.
I really should know the name of the organism since we have it here. Every couple summers someone around here dies of it. It's usually younger kids who have cuts and scrapes and swim in stagnant water.