@garry, I was in my outdoor hot tub nearly every night. I am fairly certain that I caught my mac from it. I say that because I read somewhere that one indication that it may be in there is that the ntm (mac) can cause a red itchy rash; which I did get. I also noticed that at one time our hot tub water had a 'pond' smell. I asked my hubby if he had been treating the water regularly; he said yes, but the water had not been changed in a long time. Long story short; I will not get into a hot tub, steam room, or indoor heated pool. Ever!