|MadSci Network: Microbiology|
The most common illness associated with travellers going to Mexico has been appropriatly called "Traveller's Disease". The main symptom of this disease is diarrhea. The bacteria that cause the disease belong to a family of bacteria known as the enterobacteriaceae, more commonly called enteric bacteria. These bacteria are found in the intestinal tract of many vertebrates, including humans and farm animals. Within this group, the most common bacteria to cause Traveller's Disease are certain strains of Escherichia coli (E. coli). This bacterium is common in all our intestinal tracts however some strains can produce toxins and if we become infected with these strains we may suffer from diarrhea. In countries with inadequate sewage systems and/or water treatment facilities the water can become contaminated with human and animal waste. As E. coli live in our intestines they will naturally be found in our waste (feces). The strains which produce toxins may be found in this contaminated water. The safest water source would be commericially bottled water. Choose sealed, well-known international brands whenever possible. To play it safe you should not trust any local water sources as they can be contaminated. There are two excellent web sites with more detailed information that you should visit. These sites provide, in depth, the precautions to take when travelling to countries where water supplies are suspect.
Travel Health Online has some sections devoted to traveller's disease. The Centers for Disease Control and Prevention (CDC) also has a good travel site. In particular follow this link for information on consuming food and water safely while travelling.
As an interesting aside note, you may wonder why the local inhabitants who drink the contaminated water do not become sick. Most likely they have had repeated exposure to the toxin producing E. coli stains and have aquired some immunity against these strains.
Hope this helps and that you have a safe and enjoyable trip.
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