WITH THE GREAT increase in international business and tourism, an increasing number of Americans are traveling to former out-of-the-way parts of the world and facing the potential risk of exotic diseases. However, traveling to these areas need not be dangerous if particular precautions are taken.

Three immunizations can be required by international law by particular countries - smallpox, yellow fever and cholera. None of these is presently required for entry into the United States or for travel to Europe, but the situation can change should an outbreak of one of these diseases occur in Europe.

From Oct. 26, 1977, until Aug. 28, 1978, no case of smallpox was detected anywhere in the world. On Aug. 28, the United kingdom reported a confirmed case of smallpox acquired the disease from this case was her mother. Following these two cases a number of countries began requiring a smallpox certificate from travelers arriving from the United Kingdom. Apart from the cases in England, it is hoped that the extraordinary efforts sponsored by the World Health Organization have led to the elimination of this disease from nature.

Nevertheless, it is expected that a valid smallpox certificate indicating vaccination within the previous three years will be required for entry into many countries for some time. Since there is no present risk of contracting smallpox, anyone with an accepted contraindication to smallpox vaccine, as well as pregnant women and children below age 1 year should obtain a letter of contraindication to receiving this vaccine signed by a physican on his letterhead.

Yellow fever vaccine, unlike other vaccines, must be administered by a designated Yellow Fever Vaccination Center, listed by local health departments. Yellow fever occurs in usually remote parts of tropical Africa and South America. Vaccination within the previous 10 years is required for travel to these areas and is also often required for entry into other countries for travelers arriving from yellow fever-infected areas.

As an example, travelers arriving in India directly from a yellow fever endemic area of Africa without a valid immunization certiciate for yellow fever may be denied entry or quarantined. Yellow fever vaccine should not be administered to those with altered immune states or with a documented allergy to eggs, and letters of contraindication should be given to these individuals, as well as to children below age 1 year and pregnant woman not at risk of infection.

Cholera vaccine is not thought by experts to be very effective in protecting against cholera and is considered to be secondary to proper food and water hygiene. Cholera immunization is not routinely recommended for travelers to countries not requiring it as a condition for entry. However, many countries in Asia and Africa require evidence of cholera vaccination within six months for entry.

Although not required by international regulations, a number of other vaccines are recommended for protection against diseases more prevalent in certain areas of the world. For children, routine childhood vaccines should also be up to date before traveling. Typhoid fever is endemic in much of the developing world, and vaccine is recommended for travelers to those area where it is difficult to employ a reliable nonvaccine alternative method to prevent this serious infection.

Polio is a definite hazard to travelers to the developing world and adults are particularly susceptible to paralytic complications. Since most adult American travelers will have previously had a basic primary series of either trivalent oral polio vaccine or injections of inactivated polio vaccine, only a single, preferably oral trivalent, booster is necessary.

Most travelers will have received the basic series with diphtheria and tetanus vaccines during childhood. Boosters are recommended only every 10 years to offter continued protection against these diseases.

Those considered at high risk of contracting influenza who are traveling to parts of the world where influenza is epidemic should receive the current influenza vaccine.

Certain vaccines are indicated only for very particular situations or for travel to specific remote locations. Plague is sporadically reported from the former Indochina region and Burma and from remote areas of South America and Africa, but vaccination is not required as a condition of entry by any country and is seldom recommended. Typhus occurs only in certain remote highland areas of the developing world, seldom if ever visited by Americans, and typhus vaccine is very rarely indicated.

A pre-exposure rabies vaccine series is seldom necessary for the traveler. If this is indicated, a more effective and safer human-cell rabies vaccine might best be used, but this is not yet licensed in the United States.

So-called BCG vaccine against tuberculosis is sometimes recommended for travelers to highly endemic areas for this disease, but the weight of expert opinion is against its use.

Although not strictly speaking a vaccine, immune serum globulin also known as gamma-globulin is extremely valuable in protecting against Type A viral hepatitis, probably the most common agent involved in infections hepatitis in the developing world. Travelers to hepatitis endemic aareas of the developing world who bypass ordinary tourist routes may be at greater risk of contracting hepatitis-A, and a small dose of gamma-globulia is recommended. Another indication for gamma-globulia is for those who might eat raw shellfish along the Mediterranean coast, where increasing pollution leads to contamination of these foods.

A great hazard to the traveler to the developing world is contaminated water and ice. Unless it is absolutely certain that piped water or the water in a major chain hotel is safe, it is necessary to boil for 10 minutes or chemically treat all water for drinking or making ice. Iodine compounds, such as "Potable Aqua" tablets, available in sporting-goods stores, or iodine solutions, are superior to chlorine compounds such as Halazone. Water treated with these products must stand for at least 30 minutes before it is safe to drink.

Hot water from the tap, through relatively safer than cold water, may still contain dangerous organisms and cannot be considered completely safe for drinking or brushing teeth. No available simple water filter renders water sterile of all potential dangerous organisms, and these should not be relied upon by themselves. Bottled water is generally safer than untreated tap water, but this water also may be contaminated. Well-known bottled carbonated soft drinks should be relatively safe, and hot tea and coffee, hot milk, and alcoholic beverages are safe drinks.

Certain foods are particularly hazardous and should best be avoided in the developing world. Raw fruits should be eaten only when the skin is unbroken or when they are peeled just before eating. Raw vegetables and salads should not be eaten. Only dairy products known to be hygienically prepared and property refrigerated should be eaten. Locally produced soft goat cheese, custards, cream pastries, potato salads and raw shellfish should be particularly avoided, as they are excellent vehicles for growth of dangerous organisms. Eating raw or undercooked beef, pork, sausage, or fish can possibly lead to certain parasitic infections.

Sunstroke and heat exhaustion can be avoided by abstaining from prelonged exposure to the sun or overly strennous exercise. In hot, humid climates it is important to drink more fluids and to add salt to food. Products such as "Pre-Sun" or "Pabanol" are the most effective sunscreens. Exposure to mosquitoes and other insect pests may be lessened by wearing clothing that covers the arms and legs and by applying a repellent such as "OFF" to exposed areas of the skin.

One of the greatest risks to travelers to many parts of the developing world is malaria. There has been a great resurgence of malaria in India, Pakistan and Sri Lanka, and malaria has been and remains a major hazard in tropical Africa. Earlier this year five Austrian tourists returning from a safari in East Africa died from the lethial falciparum form of malaria. Each year there are some deaths from malaria in the United States among travelers returning from malarious areas.

Malaria can be virtually prevented by the use of appropriate prophylactic drugs. Practically all cases of malaria occurring in returned travelers develop in those who have either not taken antimalarial drugs at all or who ceased taking these drugs immediately on leaving the malarious area.

Although malaria experts in other parts of the world do not always agree, the U.S. Public Health Service recommends that the drug chloroquine phospate also known as Aralen be taken in a dose of 500 mg weekly, beginning one week before a trip, while in the malarious area, and - most importantly - for at least a week after return. This dose of the drug may cause mild gastrointestinal side effects, blurred vision, or headache, but serve adverse reactions such as retinal damage have not been documented.

In some malarious areas of Southeast Asia and South America, malaria parasites have developed resistance to chloroquine, and travelers to these areas should take the drug Fansidar on a weekly basis. Unfortunately, this drug is not licensed and is unavailable in this country, but it can be obtained in most of the places where it is needed (it is recommended by the U.S. Public Health Service. Travelers intending to use this dPublic Health Service.) Travelers intending to use this drug should start taking chloroquine and continue it until they can obtain Fansidar.

Those returning from malarious areas where the relapsing vivax form of malaria is common, including India, Pakistan, and ports of West and East Africa, should receive a 14-day course of primaquine, after completing their chloroquine. Possible exposure to malaria should be mentioned when a person plans to donate blood within three years after returning from a malarious area.

Another major problem of travelers is diarrhea. Many diarrheas are noninfectious and self-limited and may arise from merely eating strange foods, nervous tension or fatigue. These often clear up on a bland diet, with particular avoidance of fats and alcohol. The important factor is treating diarrhea is to replace the lost fluids by drinking water, tea, broth, or carbonated beverages.

An ideal formula for the replacement of fluid losses from diarrhea is to prepare two separate glasses of the following: Glass I - orange or other fruit juice (8 ouncest honey or corn syrup 1 1/2 teaspoon); table salt (1 pinch). Glass 2 - boiled or carbonated water (8 ounces) with baking soda (1/4 teaspoon). Drink alternately from each glass.

Useful drugs to relieve excessive diarrhea and cramps include Lomotil, Kaopectate, or Donnatal. Lomotil is not recommended for young children and may worsen the systoms of hacillary dysentery or salmonelta food poisoning. Pepto-Bismol, taken in a dose of one ounce each half-hour until 8 doses are taken, has been found to have a favorable effect on the course of diarrhea caused by toxigenic Escherichia coli bacteria, probably the leading cause of so-called traveler's diarrhea. If diarrhea is servere, is accompanied by blood or mucus, or persists for more than three days, a physician should be contacted so that appropriate diagnosis and treatment may be carried out.

At this time, prophylactic antibiotics such as doxycycline (Vibramyci) are not recommended by experts to prevent diarrhea. Though shown to be effective in a few small-scale controlled studies, it is likely that wide-scale use of drugs of this type may lead to significant side-effects in some people. The use of such drugs as Enterovioform and Mexaform to prevent parasitic diarrhea is also not recommended as these drugs have never been proven to be effective for this indication and their use has been associated with serious neurological and eye problems. Enterovioform has been removed from the market in this country, but is and related drugs are still available without prescription in many foreign countries.

Only a handful of cases of African sleeping sickness have occurred in American travlers and most of these have been contracted in game parks in East Africa and northern Botswana. Long sleeves and trousers can decrease the risk of bites from the tse-tse fly carrier of this disease.

Schistosomiasis, or bilharziasis, occurs in Africa, the Middle East, and in certain rural areas of Latin America and the Caribbean, including Brazil, Guyana. Surinam, Venezuela, St. Lucia, Puerto Rico, Guadeloupe, and the Dominican Republic. In these areas, fresh water in streams and lakes must be considered potentially infected with Schistosomiasis and all contacts with this water must be avoided. Schistosomiasis cannot be contracted in salt water or in adequately chlorinated swimming pools.

Dengue fever has recently been widespread in the West Indies, including Puerto Rico. Though the risk of infection to travelers is small and the disease is usually mild, travelers to the West Indies should take precautions to avoid mosquito bites and should advise their physician of any acute febrile illness occurring within two weeks of return from this area. There is no licensed vaccine against dengue.

Some exotic infections, including malaria, schistosomiasis, intestinal parasites, and hepatitis, may manifest themselves months or (rarely) years after the traveler returns from an exotic area. Certainly, in the case of anyone who has had symptoms while traveling or after return, and perhaps even for the apparently healthy returnee, particular screening procedures should be performed. Especially valuable are blood counts and stool examinations for such intestinal parasites as Giardia lamblia, Extamoeba histolytics (the cause of amebiasis) and worm infections.

Malaria must always be considered as a possible cause of fever and chills, even months or for some years after return from a malarious area, particularly if appropriate antimalarial drugs have not been used. Blood smears for malaria and stool examinations for intestinal parasites should be performed by a reliable laboratory for results to be valid.

The above has been presented not to discourage travel to the developing world but to make the traveler aware of potential risks and how these can be avoided.