Food and water
- What are the common infections from contaminated food?
- What care should be taken in consuming food and water abroad?
- What are the precautions to be followed when preparing water for consumption?
- How can drinking water be filtered?
- What precautions should be associated with canned or bottled beverages?
- When is food safe to eat?
What are the common infections from contaminated food?
Among the more common infections that travellers may acquire from contaminated food and drink are Escherichia coli infections, shigellosis or bacillary dysentery, giardiasis, cryptosporidiosis, and hepatitis A. Other less common infectious disease risks for travellers include typhoid fever and other salmonelloses, cholera, infections caused by rotavirus and Norwalk-like viruses, and a variety of protozoan and helminthic parasites.
What care should be taken in consuming food and water abroad?
Contaminated food and drink are the major sources of stomach or intestinal illness while travelling and the most common sources for the introduction of infection into the body. Many of the infectious diseases transmitted in food and water can also be acquired directly through the faecal-oral route.
What are the precautions to be followed when preparing water for consumption?
Boiling is by far the most reliable method to make water of uncertain purity safe for drinking. Water should be brought to the boil for one minute and allowed to cool to room temperature. Do not add ice. At altitudes higher than 6,562 feet (2 km), for an extra margin of safety, boil for three minutes or use chemical disinfection.
Chemical disinfection with iodine is an alternative method of water treatment when it is not feasible to boil water. However, this method cannot be relied on to kill all pathogens. As a last resort, water that is uncomfortably hot to touch may be safer for drinking and brushing teeth after it is allowed to cool. However, many disease-causing organisms can survive the usual temperature reached by the hot water tap in overseas hotels.
Chlorine, in various forms, has also been used for chemical disinfection. In areas where chlorinated tap water is not available or where hygiene and sanitation are poor, travellers should note that only the following may be safe to drink:
- Beverages, such as tea and coffee, made with boiled water
- Canned or bottled carbonated beverages, including carbonated bottled water and soft drinks
- Beer and wine
How can drinking water be filtered?
Portable filters currently on the market will provide various degrees of protection against microbes. Microstrainer filters with pore sizes in the 0.1 to 0.3 micrometer range can remove bacteria and protozoa from drinking water, but they do not remove viruses. To kill viruses, users of microstrainer filters are advised to disinfect the filtered water with iodine or chlorine as described above.
What precautions should be associated with canned or bottled beverages?
Ice may be made from unsafe water and should be avoided. It is safer to drink from a can or bottle of beverage than to drink from a container that was not known to be clean and dry. However, water on the surface of a beverage can or bottle may also be contaminated. Therefore, the area of a can or bottle that will touch the mouth should be wiped clean and dry. In areas where water is contaminated, travellers should not brush their teeth with tap water.
When is food safe to eat?
Food that has been cooked and is still hot is generally safe but food should be selected with care. Any raw food could be contaminated, particularly in areas of poor sanitation. Foods of particular concern include salads, uncooked vegetables and fruit, unpasteurised milk and milk products, raw meat, and shellfish. If you peel fruit yourself, it is generally safe. Infants younger than six months should either be breast-fed or be given powdered commercial formula prepared with cooled boiled water.
Some fish are not guaranteed to be safe even when cooked because of the presence of toxins in their flesh. Tropical reef fish can occasionally be toxic at unpredictable times if they are caught on tropical reefs rather than in open ocean. The barracuda and puffer fish are often toxic, and should generally not be eaten. Highest risk areas include the islands of the West Indies and the tropical Pacific and Indian Oceans. General precautions include:
- Avoiding foods and beverages from street vendors.
- Avoiding salads.
- Avoiding undercooked or raw fish or shellfish, including ceviche.
- Drinking only water that you have boiled or treated with chlorine or iodine. Other safe beverages include tea and coffee made with boiled water and carbonated, bottled beverages with no ice.
- Eating only foods that have been thoroughly cooked and are still hot, or fruit that you have peeled yourself.
- Making sure all vegetables are cooked.
- Observing the simple rule of thumb: "boil it, cook it, peel it or forget it".
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