It isn't. I use a syringe and water with salt + baking soda, just as Gnu wrote. Apparently my sinuses don't drain well at all, and when I get a cold, it hangs on and on. Rinsing them with the salty water helps a lot.
SRS, you are right when you say the problem is some water. We need to figure out why these organisms are in some people's water, and we need to figure out how to eliminate them.