graeme_p - 7:23 am on Sep 11, 2012 (gmt 0)
Eons ago I read a newspaper article headed "If you can't drink the water, is the ice safe?" When you're visiting a Third World country (the, ahem, warm ones at least) this kind of thing is useful to know.
Depends on what the threat is. Even in (some of at least) the third world the problem is shifting away from infections to pollutants. A small amount in ice does not matter too much.
Also, I find travel health advice can be paranoid with regard to vaccines and infectious diseases (it tends to assuming you will be staying in poor accommodation, visiting high risk areas, etc.) but often does not mention risks such as parasitic worms.