Well, got back from Mexico and was zonked--Cipro does the trick--but--for all of my colleagues going abroad (and even to other states and unsure of the water), a friend of mine suggested taking grapefruit seed extract along--it's supposed to be a probiotic that kills off parasites, bacteria and other bugs. Fortraveling musicians for concerts, and auditions, take it along--but read into it first. Safe travels!!