Contaminated
food and drink are common sources for the introduction of infection
into the body. Among the more common infections that travelers
may acquire from contam-inated food and drink are Escherichia
coli infections, shigellosis or bacillary dysentery, giardiasis,
cryptosporidiosis, and hepatitis A. Other less common infectious
disease risks for travelers include typhoid fever and other salmonelloses,
cholera, infections caused by rotaviruses and Norwalk-like viruses,
and a variety of protozoan and helminth parasites (other than
those that cause giardiasis and cryptosporidiosis). Many of the
infectious diseases transmitted in food and water can also be
acquired directly through the fecal-oral route.
Water
Water that has been adequately chlorinated, using minimum recommended
water-works standards as practiced in the United States, will
afford significant protection against viral and bacterial waterborne
diseases. However, chlorine treatment alone, as used in the routine
disinfection of water, may not kill some enteric viruses and the
parasitic organisms that cause giardiasis, amebiasis and cryptosporidiosis.
In areas where chlo-rinated tap water is not available, or where
hygiene and sanitation are poor, travelers should be advised 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
Where
water may be contaminated, ice should also be considered contaminated
and should not be used in beverages. If ice has been in contact
with containers used for drinking, the containers should be thoroughly
cleaned, preferably with soap and hot water, 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, water on the outside
of beverage cans or bottles might be contami-nated. Therefore,
wet cans or bottles should be dried before being opened, and surfaces
which are contacted directly by the mouth in drinking should first
be wiped clean. Where water may be contaminated, travelers should
avoid brushing their teeth with tap water.
Treatment
of water
Boiling is by far the most reliable method to make water of uncertain
purity safe for drinking. Water should be brought to a vigorous
rolling boil for one minute and allowed to cool to room temperature—do
not add ice. At altitudes above 6,562 feet (2 km), for an extra
margin of safety, boil for three minutes or use chemical disinfection.
Adding a pinch of salt to each quart, or pouring the water several
times from one container to another will improve the taste.
Chemical
disinfection with iodine is an alternative method of water treatment
when it is not feasible to boil water. Two well-tested methods
for disinfection with iodine are the use of tincture of iodine
(Table 25), and the use of tetraglycine hydroperiodide tablets
(Globaline, Potable-Agua, Coghlan's*, etc.). The tablets are available
from pharmacies and sporting goods stores. The manufacturer's
instructions should be followed. If water is cloudy, the number
of tablets should be doubled; if water is extremely cold, an attempt
should be made to warm the water, and the recommended contact
time should be increased to achieve reliable disinfection. Cloudy
water should be strained through a clean cloth into a container
to remove any sediment or floating matter, and then the water
should be boiled or treated with iodine. Chlorine, in various
forms, has also been used for chemical disinfection. However,
its germicidal activity varies greatly with pH, temperature, and
organic content of the water to be purified, and is less reliable
than iodine.
There
are a variety of portable filters currently on the market which
according to the manufacturers' data will provide safe drinking
water. Although the iodide-impregnated resins and the microstrainer
type filters will kill and/or remove many micoorganisms, very
few published reports in the scientific literature deal both with
the methods used and the results of the tests employed to evaluate
the efficacy of these filters against pathogens. Until there is
sufficient independent verification of the efficacy of these filters,
CDC makes no recommendation regarding their use in the general
population.
As
a last resort, if no source of safe drinking water is available
or can be obtained, tap water that is uncomfortably hot to touch
may be safer than cold tap water; however, proper disinfection
or boiling is still advised.
TABLE 25. Treatment
of Water with Tincture of Iodine
Tincture
of iodine
(from medicine chest
or first aid kit) |
Drops* to be added
per quart or liter |
| Clear water |
Cold or cloudy water † |
| 2% |
5 |
10 |
*1 drop = 0.05 ml
Let stand for 30 minutes.
Water is safe to use.
† Very turbid or very cold water may require prolonged
contact time; let stand up to several hours prior to use,
if possible. |
Food
To avoid illness, food should be selected with care. All raw food
is subject to contamina-tion. Particularly in areas where hygiene
and sanitation are inadequate, the traveler should be advised
to avoid salads, uncooked vegetables, unpasteurized milk and milk
products such as cheese, and to eat only food that has been cooked
and is still hot, or fruit that has been peeled by the traveler.
Undercooked and raw meat, fish, and shellfish may carry various
intestinal pathogens. Cooked food that has been allowed to stand
for several hours at ambient temperature may provide a fertile
medium for bacterial growth and should be thoroughly reheated
before serving. Consumption of food and beverages obtained from
street food vendors has been associated with increased risk of
illness. The easiest way to guarantee a safe food source for an
infant less than 6 months of age is to have the child breast-feed.
If the infant has already been weaned from the breast, formula
prepared from commercial powder and boiled water is the safest
and most practical food.
Some
species of fish and shellfish can contain poisonous biotoxins,
even when well cooked. The most common type of fish poisoning
in travelers is ciguatera fish poisoning. Barracuda is the most
toxic fish and should always be avoided. Red snapper, grouper,
amberjack, sea bass, and a wide range of tropical reef fish contain
the toxin at unpredictable times. The potential for ciguatera
poisoning exists in all subtropical and tropical insular areas
of the West Indies, Pacific and Indian Oceans where the implicated
fish species are consumed.
Cholera
cases have occurred among persons who ate crab brought back from
Latin America by travelers. Travelers should not bring perishable
seafoods with them when they return.
*
Use of tradenames is for identification only and does not imply
endorsement by the Public Health Service or the U.S. Department
of Health and Human Services.
Reference:
CDC Health Information for International Travel
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