Many Americans have become rather adventurous travelers, eager to explore the world's more remote regions. It's their tummies, however, that often are far more timid.

The result, unfortunately, can be traveler's diarrhea, which continues to strike a large percentage of travelers to less-developed areas of the world, robbing them of vacation days or intruding on important business trips.

Methods of treating diarrhea effectively have been under medical review in recent years, and other medical developments affecting travelers include the introduction of new drugs for the prevention of malaria and typhoid fever, which continue to be health threats in large parts of the world.

Between 20 and 50 percent of travelers heading for areas considered at high risk for diarrhea can expect to be affected by the illness, according to Martin S. Wolfe, a physician and tropical medicine specialist who heads the Traveler's Medical Service of Washington, a private clinic offering immunizations and health consultations for travelers. Wolfe's report on the latest methods of treatment for diarrhea appeared in the June 20 issue of the American Journal of Medicine.

The high-risk areas for diarrhea, says Wolfe, are Latin America, Africa, Asia and the Middle East -- that is, a substantial portion of the international map.

To protect yourself when visiting these areas, you should be familiar with the standard dietary "no-no's" -- such as don't drink the water or eat uncooked vegetables. But you also might want to pack along medication should diarrhea strike, as it can even when you are being cautious. Germs can cling for hours to dishes, glassware and eating utensils that have not been properly washed and dried.

At least two nonprescription medications -- marketed as Pepto-Bismol in liquid and tablet form and Imodium A-D caplets -- have proved effective in quickly alleviating the symptoms of traveler's diarrhea. Both are among the remedies recommended by Wolfe, who also is the tropical medical consultant to the State Department.

Malaria & Typhoid

Malaria and typhoid fever are far more serious ailments, but important advances in the prevention of both have been introduced this year:

Malaria: A new anti-malaria drug called mefloquine, slowly becoming available to doctors this year, has been shown to be effective against malaria parasites that have developed a resistance to earlier anti-malaria drugs, says Wolfe. The trade name is Lariam.

This is very good news for travelers, since resistance to older drugs has spread to most areas with malaria, according to the Centers for Disease Control in Atlanta. Malaria occurs in large parts of Central and South America, Africa (south of the Sahara), South Asia, the Middle East and islands of the South Pacific.

However, because of mefloquine's possible adverse side effects, Wolfe does not recommend administering it to children weighing less than 30 pounds, pregnant women, persons using certain heart medications or individuals with a history of epilepsy or psychiatric disorder. The dosage is determined by the length of stay in a malaria area and must be prescribed by a doctor.

Mefloquine has been hard to obtain in recent weeks, according to Wolfe. Paul Oestreicher, a spokesman for the manufacturer, Hoffmann-La Roche, says supplies of the drug should become sufficient very soon.

Typhoid fever: An oral vaccine against typhoid fever, previously available in Europe, was licensed this year for use in the United States. Until now, typhoid vaccine in this country was administered by injection. Because of the oral vaccine's comparative efficiency and minimal side effects, says Wolfe, it should be the vaccine of choice for travelers going to an area where the disease is prevalent -- Africa, Asia and Central and South America.

However, the vaccine -- Ty21a -- should not be administered to children under age 6 or anyone with an acute fever or stomach ailment, anyone taking sulfa drugs or antibiotics or anyone who has AIDS. Pregnant women should receive the vaccine, says Wolfe, "only if clearly needed for protection." A dosage is four capsules, available from a doctor. They are taken one at a time every other day for four doses.

The malaria drug and Ty21a vaccine should not be taken simultaneously. This means that travelers going to destinations where precautions against both malaria and typhoid are recommended must plan ahead. If possible, says Wolfe, the dosage for typhoid fever should be completed at least seven days before beginning the anti-malaria series, which continues during the length of the stay in a malaria area and for four weeks after departure. If you must choose between the two, the malaria series should take precedence, says Wolfe.

Traveler's Diarrhea

So far, there are no vaccines against traveler's diarrhea, and really no assured way to prevent its occurrence -- which can happen anywhere, not just in high-risk areas. Southern Europe and some Caribbean islands pose a moderate risk, says Wolfe, and the United States and Canada are not exempt, although the risk is considerably less.

You can get it by eating contaminated food, drinking contaminated water or shaking the contaminated hands of an infected person. The symptoms, says Wolfe, include frequent loose bowel movements, nausea, bloating, abdominal cramps and fever. If bloody stools, vomiting or high fever occur, the illness could be serious, and a doctor should be consulted. Also, if diarrhea persists for more than two days, see a doctor.

Overindulgence, exhaustion, jet lag and high altitude may also produce a noninfectious form of diarrhea, says Wolfe.

If you are going to get traveler's diarrhea, it probably will be in the first week of your trip. This is because most forms of the illness are caused by bacteria or viruses, says Wolfe, and their incubation period is short. The young tend to be more susceptible than older travelers.

Standard precautions against traveler's diarrhea are probably familiar to most travelers, but they bear repeating. In high-risk areas:

Don't drink tap water, or use it to brush your teeth. Stick to bottled water, carbonated beverages (which, says Wolfe, can inhibit growth of bacteria), beer, wine and drinks made from boiled water, such as tea and coffee.

Avoid salad greens and other raw vegetables that may have been washed -- ineffectively -- under contaminated water.

Eat only fruit that you peel yourself with clean hands.

Make sure meat, fish and poultry have been well cooked.

Avoid unpasteurized milk and other dairy products, including ice cream sold by street vendors.

Don't take ice in your drinks unless you know it was made from purified water.

Skip the hotel's buffet lunch that may have sat under the sun for hours.

Travelers may also want to consider taking the familiar pink Pepto-Bismol tablets as a preventative. According to Wolfe, studies show that the pink tablets -- taken two tablets at a time, four times daily and for up to three weeks -- can be a "safe and effective" means of reducing the occurrence of traveler's diarrhea. You can cut your chances of falling ill by 65 percent.

Pepto-Bismol should not be used if you are taking aspirin on a regular basis, says Wolfe, and the manufacturer suggests also that pregnant women and nursing mothers should seek advice from a health professional.

Should you come down with diarrhea despite your best efforts, the current remedies of choice are Pepto-Bismol -- in liquid rather than tablet form -- and Imodium A-D, a caplet sold over the counter in drugstores. Wolfe says he advises his clients to carry Imodium A-D. The caplets, marketed by McNeil Consumer Products Co., contain an antimotility agent that relieves the symptoms of diarrhea by slowing intestinal movement.

The caplets should not be taken by children under the age of 6, according to the distributor, or by anyone for more than two days unless directed by a physician. Do not take them if a bloody stool or a high fever accompanies the diarrhea. Pregnant women, nursing mothers and persons having a history of liver disease should consult their doctor about using them.

If diarrhea persists or is severe, a doctor may take the additional step of prescribing an antibiotic such as Bactrim. Hoffmann-La Roche, the manufacturer, says Bactrim can stop the symptoms of diarrhea "in as little as an hour" when used with one of the over-the-counter anti-diarrheals, such as Imodium A-D. Used alone, Bactrim can "shorten the course of TD {traveler's diarrhea} from a typical three- to five-day attack to one lasting only a day or a day-and-a-half."

Some travelers may want to carry a supply of Bactrim or another antibiotic with them, but Wolfe does not recommend this practice unless you are headed for a remote destination where medical treatment may not be available. In areas where medical aid is accessible, he advises seeing a doctor in cases of prolonged or severe diarrhea. The doctor can then determine which is the most appropriate antibiotic for treatment.

Bactrim's possible adverse effects, says Hoffmann-La Roche, include allergic skin reactions. If any occur, the drug should be discontinued.

Other nonmedicinal steps can help you get through a bout of diarrhea more comfortably. With diarrhea, dehydration is a possibility. To combat it, Wolfe recommends drinking canned fruit juices and caffeine-free soft drinks and eating salted crackers. Orange juice and bananas help maintain potassium levels. If possible, avoid milk and other dairy products, he says, because they can aggravate diarrhea.

The Traveler's Medical Service of Washington, which Wolfe heads, is one of several clinics in the Washington area that specialize in the medical problems of travelers. Others are operated by George Washington and Georgetown university hospitals. At the clinics, travelers can obtain necessary immunizations for travel abroad, obtain pre-trip advice on health concerns and receive treatment for exotic infections they might acquire while abroad.

For information:

Traveler's Medical Service of Washington, 2141 K St. NW, Suite 408, Washington, D.C. 20037, 466-8109.

Traveler's Clinic, George Washington University Medical Center, 2150 Pennsylvania Ave. NW, Room 5-403, Washington, D.C. 20037, 994-8466.

International Health Service, Georgetown University Hospital, 3800 Reservoir Rd. NW, Washington, D.C. 20007, 687-8672.

Foxhall Immunizations, 3301 New Mexico Ave. NW, Suite 331, Washington, D.C. 20016, 362-4467. A private clinic.

Seasickness Aid

Cruise passengers may want to try a new device called AcuBand that uses the principles of acupuncture in an attempt to relieve seasickness and other motion discomfort. The device, a narrow strap with a centrally placed button, is worn on each wrist. The button, explains AcuBand, exerts a gentle pressure on the "nai-kon" point, which is the pressure point affecting nausea.

AcuBand is being marketed to travelers who want a motion sickness aid that does not involve the use of drugs, some of which can cause drowsiness or sharply limit the use of alcohol during the cruise. AcuBands have no medical side effects. Their only drawback is appearance. They look like very cheap wristwatches. The straps -- which come in red, yellow, navy and beige -- can be worn before the trip begins or at the onset of discomfort.

The company says tests conducted over the past four years have shown the AcuBand straps to be effective. The validity of this claim, however, is difficult to assess because the test data was not made available.

Spokespersons for the four local traveler's clinics listed above either had not heard of AcuBand or had no opinion. A local acupuncture clinic also was not aware of the device. The Norwegian Cruise Line, one of the large cruise lines sailing the Caribbean, also has no experience with it, says Rhonda Broder-Dunlevy, the medical director.

However, Mike Silverman, owner of Traveler's Checklist, a mail-order travel accessory firm in Connecticut, says he has sold "hundreds of them" and has received only one complaint. "That's a pretty good record."

AcuBand says the straps have been used by sailors, fishermen, airplane pilots, train commuters and children in the family car. The straps are adjustable to any wrist size.

The device was created by Ann Alessandroni and Richard Griffith, both of whom are recreational sailors. Alessandroni, who suffered from seasickness, read about the pressure point for motion sickness in an acupuncture book. At first she used her fingertips to control the nausea when sailing. Then Griffith, whose wife also experienced severe bouts of seasickness, devised the strap so that the pressure could be maintained.

Traveler's Checklist sells the bands for $14.95 a pair, plus $1.75 for shipping. Contact: Traveler's Checklist, 335 Cornwall Bridge Rd., Sharon, Conn. 06069, (203) 364-0144. For other outlets, including some pharmacies, contact: AcuBand, (201) 842-8118.