|MadSci Network: Medicine|
Actually, there are a number of organisms that can affect us that live in the water we drink in Mexico (or other countries, or even situations - like flooding-). These would include varieties of: *protozoans - (single celled organisms) Amoeba (amoebic dysentery) Giardia *bacteria - E. coli Salmonella Camphylobacter *Viruses These can all affect our digestive systems - symptoms would include vomitting and diarrhea, intestinal cramping, flu-like symptoms. People that live/are born in areas where the water is contaminated are often immune to the disease. Their immune systems have been exposed to the organisms for a long time in small amounts, and the antibodies produced against the organism by the immune system most likely protects them from the disease.
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