I work in poison control. I wouldn't say it has much in common with either epidemiology or infection control. But it probably would be closer to epidemiolgy if I stretched it a bit.
As far as poison control education goes, you don't need a masters, although it wouldn't hurt, of course. A few people I work with have masters degrees...one has an MSN, one has a masters in chemisty, one in something else science related.
I'm trying to figure out what I want to do at this point, too. Thinking of NP vs. PA vs. MD vs. PharmD, lol.
I really like poison control. It's very interesting. We got to learn a lot of science I didn't know before. I also enjoy telling people what to do!