Ok, based on those numbers, I'm not going to get a flu vaccination for myself or my kids ever again. Because the number of people who get and then die from the flu is pretty low, why should I worry about it?
Of course, the reason the number is as low as it is, probably has something to do with the fact that many people are vaccinated. Just like the numbers for Legionnaire's may be low because most people's water heaters are set at an appropriate temperature.
Personally, I do worry about it, but not obsessively so. After we've been away for a while (and had the water heater switched off), I'll run quite a bit of water through it to flush it out. Then I'll turn it on at near max (whatever that may be, 160, 180 degrees). I leave it that way for a few days, making sure everyone knows to be extra extra careful when using the hot water. After a few days, I'll turn it down closer to 140 (probably a tad higher). If I stayed in the house long enough, I'd probably repeat this once or twice a year, just to kill any baddies that tried to start growing in there. Maybe not the best way to go about it, but that's just what I do.