Occasionally the diarrhea can be from protozoa or worm infections. Other protozoa that cause intestinal infections include the amoeba Entamoeba histolytica, cryptosporidium and cyclospora. In contrast, the serious infections include bacillary dysentery, amoebic dysentery, and cholera. According to the Pan-American Health Organization, cholera is still spreading over Latin America, with 1.3 million cases since the last epidemic began in Peru in January 1991. To keep ourselves down to earth, let's call the great event Traveler's Diarrhea when there is at least twice the normal number of bowel movements, whether soft or watery or bloody.
Dehydration is possible.
Dehydration is a serious consequence, with death occurring in as quickly as 24 hours with cholera. Most diarrheal diseases are easily preventable and actually are also easily treated once diagnosed. Among the primary measures to prevent gastrointestinal illness are washing your hands, getting specific vaccines and prophylactic medications. There are great vaccines against typhoid fever, which is caused by salmonella, and for the Hepatitis A virus. The vaccine for cholera that is available in the USA is not very good, whereas there is a more reliable and longer-acting one available in Europe.