Answer: Traveler's diarrhea can be due to a virus or parasite, but in four out of five cases, it's due to a toxic form of E. coli bacteria. According to the Centers for Disease Control and Prevention, it affects 20 percent to 50 percent of international travelers, or an estimated 10 million folks each year. This number is growing. It usually occurs within the first week of travel, but may occur at any time during the visit, and may not even begin until you've returned home.

Traveler's diarrhea is most common in Latin America, Africa, the Middle East, and Asia. While it can affect anyone, those at highest risk are young adults, those with a weakened immune system, those with some preexisting disease of the colon such as ulcerative colitis or Crohn's disease, and persons taking acid-blocker medication or antacids (stomach acid helps to kill the infectious organisms). While it may not be a pleasant thought, the main way that we get traveler's diarrheal infection is from fecally (i.e., stool) contaminated food or water.

It usually produces a watery diarrhea with at least 4 to 5 bowel movements per day, cramps, and low-grade or no fever. Most cases are not serious and will resolve within a few days - even without specific treatment.

As you've discovered, Pepto Bismol works great for traveler's diarrhea. I'd recommend packing Pepto Bismol tablets in your suitcase for future travel (as long as you're not pregnant or nursing). It works as both a preventive and curative measure for most cases. Imodium and Kaopectate will control diarrhea symptoms, but don't help kill bacteria. Remember to drink fluids like Gatorade to replace lost fluids and electrolytes.

Q: Is it helpful to get the shingles vaccine if I've already had shingles?

A: Yes. The Zostavax vaccine, currently approved for folks 60 and older who have a healthy immune system, can cut the risk of having an outbreak of shingles (a reactivation of the chicken-pox virus) at least in half, even if you've had a previous outbreak. Furthermore, in folks who receive the Zostavax vaccine and end up getting shingles, there's a two-thirds reduction in the incidence of "post-herpetic neuralgia," a painful, often chronic nerve pain that typically follows a bout of shingles. The vaccine is a preventive effort; it is not approved for the actual treatment of shingles or post-shingles nerve pain.

The Zostavax vaccine works by using a controlled dose of a live, weakened form of chicken-pox virus to stimulate an immune response against the chicken-pox virus. The amount of virus needed to stimulate an immune response in older folks is 14 times greater than what is used to vaccinate children. By revving up one's immune system against the dormant chicken-pox virus, the Zostavax vaccine can cut the chances of an outbreak about 50 percent. Zostavax is being studied in folks 50 years of age and older.