Friends and family so often asked Dr. Charles E. Davis, a specialist in microbiology and infectious disease, how to avoid getting sick when they travel abroad, he decided to put all his advice in one place. The result, "The International Traveler's Guide to Avoiding Infections," was released by Johns Hopkins University Press. Here's an edited chat with Davis:

What steps should you take before you depart?

If you're going to a developing country, visit a travel clinic four to eight weeks before you travel to get any immunizations you may need. You can find one on the websites of the International Society of Travel Medicine or the American Society of Tropical Medicine and Hygiene. Make an appointment with your primary care physician for an exam and for any routine immunizations like a DPT update, hepatitis A and B, and influenza; if you get these done at travel clinics, you run the risk of paying out of pocket.

The International Traveler’s Guide to Avoiding Infections
The International Traveler's Guide to Avoiding Infections ( johns hopkins press )

Is travelers insurance worth getting?

Depends on your destination, your age, your health, what you're doing and whether or not you're a gambler. Some good (insurers) I recommend are FrontierMEDEX; International SOS; and CSA Travel Protection. You can comparison-shop at TravelGuard.com or InsureMyTrip.com.

What should you pack?

For any overseas trip, I recommend taking along self-treatment for traveler's diarrhea -- loperamide, known by the brand name Imodium here, and an antibiotic, the most common being ciprofloxacin. Other things to pack: Band-Aids and topical antibiotics to treat minor wounds; water purification tablets; sunscreen; and insect repellent with 30 to 50 percent DEET. Hikers should bring a full suture kit.

While you're visiting a country, what should you keep in mind?

Avoid tap water and ice in developing countries as well as salads and buffets, which bacteria just love. A good rule to follow: Boil it, peel it or forget it.

And once you return?

If you were away longer than three months in a developing country, had done aid work or were exposed to needles or fresh water, or had been ill or had sex, I'd recommend doing a screen for various infections at a travel clinic.

-- Emily Brennan, New York Times