The International Society for Travel Medicine (ISTM) website at
a particularly useful link to non-ISTM information resources on its web site, which is
Assigning countries to one of three zones can roughly calculate disease risk.
Health risk in these countries is the same as expected here at home. In fact Zone I
includes the United States and Canada, the nations of northern Europe (to include
France), and New Zealand and Australia. Advise persons visiting these countries to
obtain routine age specific and special risk immunizations.
There is an increased health risk in these countries which include European countries
bordering the Mediterranean (except France), all islands of the Caribbean (except Haiti
and the Dominican Republic), Israel, South Africa, Japan, Eastern Europe, and the Soviet
Union. Besides the expected illnesses of Zone I, there is increased exposure to the food-
and water-borne diseases. Immunization with typhoid and hepatitis A is appropriate.
Countries in this highest risk area include all nations in Central and South America,
Mexico, the Dominican Republic, Haiti, and all nations in Asia and Africa, except Japan,
Israel, and South Africa. In addition to the exposure risks of Zones I and II, the traveler
will encounter significant exposure to insect-borne illness, as well as increased risk to the
food- and water-borne diseases. Immunize with typhoid and hepatitis A as in Zone II and
additionally Japanese encephalitis or yellow fever if appropriate and advise the traveler to
take additional insect protection precautions.
Disease Prevention Strategies
The above three referenced lectures contain information of the utmost importance with
regard to prevention of disease.
Water source reliability is difficult to assess. Consider plumbing to be inadequate in all
developing countries and suspect in many developed ones. Bottled water may be
"counterfeit." The safest way to avoid unsafe bottled water is to purchase carbonated
water ("with gas") as bottlers of carbonated water usually have the ability to purify water
and the acidic pH will discourage bacterial and viral growth. Even the US bottled water