Drinking water safety for travelers

Water purification tactics
Boiling water is generally the most effective way to remove parasite contamination. Maintain a rolling boil for at least one minute (longer at higher altitudes, where the boiling point may be lower). Let the water cool itself slowly without adding ice. Allow any sediments and particles to settle before drinking, and then decant the water from the top into another container.

Commercially available iodine or chlorine tablets kill bacteria and viruses, but are ineffective against some protozoa (like cryptosporidium). Iodine is the more effective of the two solutions, but is not recommended for long-term use, especially by pregnant women or travelers with a history of thyroid problems. Potable Aqua, composed of the iodine compound tetraglycine hydroperiodide, is the most popular brand of water purification tablet. Read directions on all tablets systems for tablet-water ratios and dissolving times; 20 minutes or more may be required for the tablets to dissolve completely, especially in colder water.

If you do not have tablets, two drops of common chlorine bleach in a quart of water will help as a last resort.

The SteriPEN uses ultraviolet light to kill bacteria, viruses and protozoa. It's portable, effective and powered by AA batteries, making it convenient to bring just about anywhere. Its relatively hefty price tag is worth it if you frequently visit areas with questionable water quality, particularly if you plan an extended stay.

Outdoor stores like Cabela's carry water filters and purification systems. It is essential that the filter system you choose is suited to your needs. A filter with an insufficiently small pore size, or one that is not designed to filter viruses, may permit some contaminants to get through. The most effective strategy is to buy a system that combines filtering with chemical purification — or make one yourself by using both a filter and an iodine treatment.

For more tips on making water safe to drink, visit the CDC's Web site.

What to do if you get sick
Symptoms of water-borne illness generally include diarrhea, vomiting, nausea, fever, aches and/or chills, according to the World Health Organization (WHO). These symptoms will usually clear up on their own after a few days; if they worsen or are very severe, seek medical attention. Otherwise, try to stay hydrated with sports drinks, boiled or bottled water, or other safe fluids (steer clear of alcohol and caffeinated beverages, both of which can make dehydration worse). Oral rehydration salts and anti-diarrheal medications may also be helpful. You can find more tips and remedies in our article on traveler's tummy.

When to damn the torpedoes
If the locals are drinking the tap water without ill effect, there is no known occurrence of giardiasis, and you are going to be staying in one location for four weeks or more, you may want to drink the water to allow your body time to acquire some of the local microbes. Start slowly and allow your body time to adapt.

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