Travel the world.

John D. Wilson, M.D.
1200 Hilyard St., Ste. 560
Eugene, Oregon 97401 USA
fax 541.485.7702


the short version

1.  Regarding food: if you can't cook it, boil it or peel it, then forget it. No frozen desserts, such as ice cream, sherbet or popsicles. No raw vegetables. No milk products.
2.  Regarding drink: bottled drinks or boiled, filtered or chemically disinfected water only. No ice in your drinks.
3.  If you have diarrhea despite your best efforts at prevention, try to distinguish between ordinary Travelers’ Diarrhea and dysentery (dysentery signs are one of: blood mixed with diarrhea, fever, abdominal pain, vomiting or lack of response to antibiotics). See our handout on diarrhea treatment.

the long version

Contaminated food and drink are common ways to catch several infections, most commonly TD (Travelers’ Diarrhea), giardia and hepatitis A. Other less common food and waterborne infectious disease risks include typhoid fever, other salmonella, shigella, campylobacter, amoebae, cholera, several viruses and a variety of one-celled and worm-like parasites.

WATER which has been adequately chlorinated using minimum recommended waterworks standards as practiced in the United States will give protection against waterborne diseases. However, chlorine treatment alone used by individuals for water disinfection is hard to standardize and will not reliably kill some viruses, giardia and amoebae. In areas where chlorinated tap water is not available or where hygiene and sanitation are poor, the only safe drinks are:

  1. beverages, such as tea and coffee, made with boiled water

  2. canned or bottled beverages, including bottled water and soft drinks which you open; carbonated beverages help ensure beverage safety
  3. beer and wine

Where water safety is uncertain, ice and containers for drinking should also be considered contaminated; ice should not be used in beverages. If ice has been in contact with a container to be used for drinking, all surfaces should be thoroughly cleaned after the ice has been discarded. It is safer to drink directly from a can or bottle of a beverage than from a questionable container; however, the outside of the can or bottle might be contaminated. Wet cans or bottles should be dried before opening and surfaces which are in direct contact with the mouth should first be wiped clean. Some travelers are so cautious that they drink only carbonated beverages and insist upon personally opening all bottles, thus proving to themselves that the bottle has not been refilled by an unscrupulous eating establishment. Where water may be contaminated, travelers should not brush their teeth with untreated tap water.

WATER TREATMENT   Boiling is the most reliable method to make water of uncertain purity safe for drinking. Water should be brought to a vigorous boil and allowed to cool at room temperature; do not add ice. For an extra margin of safety at very high altitudes where boiling temperatures are lower, boil for several minutes or use chemical disinfection. To improve the taste, add a pinch of salt to each quart or aerate by pouring the water several times from one container to another after cooling.

Chemical disinfection with iodine is an easy, reliable method of water treatment when boiling is not feasible. Two well tested methods are:

  1. tincture of iodine; our iodine water disinfection kit is provided and additional kits are available for purchase at our front desk, and

  2. tetraglycine hydroperiodide tablets (Globaline, Potable Aqua, Coghlan's, etc., available from many pharmacies and sporting goods stores). Follow manufacturers’ instructions.

The tincture of iodine method is preferred over the tablet method because no dissolving time is needed, greater availability throughout the world, greater stability in heat, longer shelf life and lower cost. If water is cloudy or cold, the amount of iodine preparation and/or the recommended contact time should be doubled to achieve reliable disinfection. Cloudy water should be strained through a clean cloth into a container to remove any sediment or floating matter before treatment with iodine or by boiling. Pregnant women should not use iodine disinfection.

There are a variety of portable filters currently on the market which, according to the manufacturers, will provide safe drinking water. Although iodine impregnated resins and the microstrainer filters will kill and/or remove many germs, very few published reports adequately evaluate the efficacy of these filters against waterborne pathogens, especially viruses. (See companion handouts: WATER DISINFECTION or the Backpacker magazine field trial available in our office for more information about water filters).

water disinfection with tincture of iodine
water 2% tincture**
for small amounts (quarts)
7% (strong) tincture**
for large quantities/groups (gallons)
clear 1/2 cc per quart 1/2 cc per gallon 8-10 ppm
cloudy/cold* 1 cc per quart 1 cc per gallon 16-20 ppm
*very turbid or very cold water may also require prolonged contact time
**let stand at least 30 minutes before use, preferably several hours if possible

As a last resort, if there is no sure source of safe drinking water, tap water that is uncomfortably hot to touch (140 deg F; take a thermometer?) is usually safe. After allowing such hot water to cool to room temperature in a thoroughly cleaned container, it might be used for brushing teeth and drinking.

CHOOSING FOOD with care will help avoid illness. Any raw food may be contaminated. Particularly in areas where hygiene and sanitation are inadequate, the traveler should avoid salads, uncooked vegetables, unpasteurized milk (consider avoiding any milk products). We advise eating only cooked food which is still very hot when served, or fruit peeled by the traveler. Undercooked and raw meat, fish and shellfish may carry various intestinal germs. We advise against frozen desserts, such as ice cream, sherbet or popsicles.

TRAVELERS' DIARRHEA (TD) causes sudden liquid stools, nausea, bloating, a sense of urgency to have a bowel movement, perhaps mild abdominal cramps and a general ill feeling. Ordinary TD usually occurs during travel or soon after returning home, is self-limited and is usually more an inconvenience rather than a serious disease. The chance that a traveler is going to come down with TD is in the range of 20 to 40 percent. The most important determinant of risk is the destination of the traveler. High risk destinations include most of Latin America, Africa, the Middle East and Asia. Intermediate risk destinations include Southern European countries and a few Caribbean islands. Low risk destinations include Canada, Northern Europe, Japan, Australia, New Zealand, the United States and other Caribbean islands. There is no information to support any noninfectious cause of TD such as changes in diet, jet lag, altitude, fatigue, etc.

PREVENTION of TD  Possible approaches to prevention of TD include careful food and drink preparation, use of medications other than antibiotics and preventive antibiotics.

Meticulous attention to food and beverage preparation, as mentioned above, can decrease the likelihood of developing TD, however most travelers have difficulty observing the needed dietary precautions. No available vaccine is available for TD and none is expected soon.

Several non-antibiotic medicines have been advocated for prevention of TD. Controlled studies indicate that preventive use (i.e. use before the onset of diarrhea) of diphenoxylate (brand name Lomotil) actually increases the incidence of TD in addition to producing other undesirable side effects. Antimotility agents (eg diphenoxylate and loperamide, brand name Imodium) are not effective in preventing TD. No data support the preventive use of activated charcoal. You may want to review the literature supports the use of probiotics, available at many health food stores.

Preventive use of bismuth subsalicylate (the active ingredient of Pepto-Bismol), 2 oz four times daily or 2 tablets four times daily, has decreased the incidence of diarrhea by about 60 percent in several placebo controlled studies. Side effects include temporary blackening of tongue and stools, occasional nausea or constipation, and rarely, ringing or buzzing in the ears. There is not enough information to exclude risk from using large doses of bismuth subsalicylate for a period of several weeks or more. Bismuth subsalicylate should be avoided by persons with aspirin allergy, those who are on anticoagulant therapy or persons taking probenecid or methotrexate. In people already taking salicylates (aspirin and others) for arthritis, large doses of bismuth subsalicylate can produce toxic serum salicylate concentrations. Bismuth subsalicylate appears to be effective prevention for TD, but is not recommended for periods of more than three weeks. Further studies of the effectiveness and side effects of lower dose regimens are needed.

In the past, the information indicated that antibiotics do not prevent TD and are not recommended for prevention. Rifaxamin (brand name Xifaxan), a new non-absorbed antibiotic, has recently become available and has been shown to prevent TD. It is expensive, but is an option. The recommendation that travelers rely on sensible dietary practices is justified by the excellent results of early treatment of TD. See companion handouts “Treatment of Travelers’ Diarrhea and Dysentery”, “Water Disinfection” and the Backpacker article on water filters.

(Adapted from Health Information for International Travel, Centers for Disease Control)

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  John D. Wilson, M.D. 1999-2018; Last Update 2/26/2018