Food and Water Precautions
Travellers may find themselves exposed to the organisms that can cause travellers' diarrhoea. These organisms are all spread by human/animal faecal contamination of food, water or surfaces and are ingested during eating, drinking or hand to mouth contact.
The risk of travellers diarrhoea can be reduced by practising good food, water and hand hygiene.
Hand hygiene when eating and drinking is very important.
- Where possible, wash hands prior to handling food, eating and always after using the toilet.
- Handwashing facilities may be poor or not available when travelling, therefore it is advisable to carry sanitising gel or hand wipes at all times.
There are some general rules of food and water precautions. While it may not be practical to follow all of these rules, all of the time, applying them where possible will reduce the risk of travellers' diarrhoea.
- Ensure that clean dishes, cups and utensils are used; use alcohol wipes to clean them if necessary.
- If using street vendors, where possible, choose food that is freshly cooked to a high temperature and served immediately while still hot.
Freshly prepared thoroughly cooked food, served piping hot, including meat and vegetables, is generally safe. Avoid leftovers or food that may have been left uncovered for any length of time.
Note the following:
Meat should be thoroughly cooked and eaten hot.
- Leftovers and reheated meat should be avoided.
Fish and shellfish can be hazardous even if well cooked. Local advice about seafood should be sought, but when in doubt it is best avoided.
Only consume pasteurised milk/milk products.
- Unpasteurised milk should be boiled.
- Cheeses and ice cream are often made from unpasteurised milk. When in doubt these should only be bought from larger well established companies where quality can usually be assured.
Only eat thoroughly cooked vegetables.
- Salads and fresh herbs (including in drinks) should be avoided.
- Avoid buffet style food and instead choose freshly prepared, thoroughly cooked food that is served piping hot where possible.
Peel fruit, including tomatoes.
- Berries, in particular raspberries, may be a source of Cyclospora (a parasite) infection. They are difficult to wash and best avoided.
Water can contain not only visible debris and harmful microorganisms, but also chemical pollutants.
Water should only be drunk if its purity is known. This also applies to water used for making ice cubes and cleaning teeth. Water that is bottled (with intact seal), boiled, chemically disinfected or passed through a reliable filter is usually safe, as are hot tea and coffee, beer, wine and spirits.
- Milk should be boiled unless you are sure that it has been pasteurised.
- Freshly squeezed fruit juice may be made with unwashed fruit; juice from sealed cartons is preferable.
This is the most reliable method of removing microorganisms, but will not remove debris. A rolling boil for one minute achieves adequate purification. Water should be boiled for 3 minutes at altitudes above 2000 m (6562 ft) where water boils at a lower temperature.
Water purified in this way should be cooled and covered to avoid contamination after boiling.
If water is not boiled, a combination of techniques to disinfect water should be used, and can include the use of filters (ceramic, carbon, membrane), halogens, chemical disinfectants and/or UV radiation.
Filtration traps and removes debris and microorganisms from water. Filtration is useful for those who may only have access to brackish water such as rivers and streams, as filters remove debris. Filter pore size largely determines how effective a device will be, although micro-organisms will also stick to the filter material. Filter pore sizes between 0.1-0.4 µm are usually effective at removing bacteria and parasites but may not adequately remove viruses.
If this type of filter is used, filtered water must also be chemically treated or boiled.
A wide variety of filters are available and prices vary accordingly.
Manufacturers’ literature should always be checked prior to use.
Filtration combined with Chemicals
Some modern filters incorporate a method of chemical disinfection to increase their effectiveness. Such filters should be replaced after a specified volume of water has been treated, although this can be difficult to keep track of.
Chlorine Dioxide is available in tablet or droplet form and is cheap and effective (e.g. Aquamira). Chlorine Dioxide will kill bacteria, viruses and some parasite cysts in water. Follow directions on the pack for effective use. It is ineffective against the parasite Cyclospora.
Halogens are cheap and easy to use and may be the method of choice for those on the move such as backpackers and expeditioners. Halogens are readily inactivated by organic debris, which should be removed first. They inactivate bacteria and viruses but not parasite cysts. The main halogens used are:
Chlorine, (usually as Sodium or Calcium hypochlorite) is the most commonly used disinfectant in municipal water supplies worldwide and is non-toxic.
- Iodine (no longer recommended)
Since Oct 2009, EU directives have banned iodine for this use due to toxicity concerns. It is no longer available in EU countries for the purpose of water purification.
Ultraviolet (UV) Radiation
Ultraviolet (UV) light can destroy bacteria viruses and some parasite cysts. The effectiveness of this means of water purification depends on the UV dose and exposure time used. This method requires that the water being treated is clear as the effectiveness of the device may be limited in water that is very cloudy or has a high level of debris in it. Battery-operated pen devices that deliver a metered, timed dose of UV are available and may be an effective means of disinfecting small amounts of clear water.
Salt (Sodium Chloride) Electrolysis
A hand-held device works by passing a small electrical charge is passed through a solution (using the device) generating the production of oxidants, including hypochlorite. This solution is then added to untreated water and according to the manufacturers inactivates bacteria, viruses and some parasites. It is unlikely to be effective against the parasite Cyclospora.
Outdoor and Adventure Holiday Shops and Pharmacists
Equipment for sterilising water and water filters can usually be purchased at outdoor sports, camping and adventure shops. The manufacturers leaflet should be consulted prior to use to ensure the product eliminates all pathogens that you maybe at risk from. Chlorine preparations can often be obtained from local pharmacies. Filters for sterilising water must not be confused with cheaper versions (sometimes available in supermarkets) designed only to remove odour and chlorine from domestic water.