Due to differing climates, flora and fauna, standards and styles of living, it is easy to see why different diseases are endemic (constantly present) in different countries. However, only the infectious diseases pose a risk to the international traveller. The risk is relatively small if the traveller takes proper precautions, such as observing food hygiene, protecting against insect bites, and getting immunized against certain infectious diseases.
A distinction should be made between immunizations required by law by countries for entry into their territory and immunizations recommended by the World Health Organization (WHO) for general protection against certain diseases.
Immunization required by law
Each country draws up its own requirements to protects its population from diseases that travellers may bring from other countries. It is usual for a country to have at least two lists:
a) a list of disease which incoming travellers needs to be immunized against, and
b) a list of the endemic countries where the travellers coming from or passing through require immunization.
Nowadays, since the eradication of smallpox, the only disease for which immunization is internationally required is yellow fever. But a few countries require immunization certificates for other disease as well. For example, Saudi Arabia requires pilgrims to Mecca to be immunized against meningococcal meningitis (an infection of the membrane covering the brain).
Requirements of country you visit
Now, if you are traveling to a country which, say, typhoid fever is endemic, that country may not require you to be immunized against the disease. This is because the country is, after all, only interested in protecting people against disease which they do not already have. But it is certainly in your interest to be immunized against typhoid before going there.
So the best way to find out for a particular country what its immunization ‘requirements’ are – what is required by the country’s law and what is advisable for you – is to ask your travel agent, or the WHO Representative.