Quick, name a disease that's a problem in developed countries as well as in the developing world--and for which the Centers for Disease Control and Prevention issued a June warning to travelers.

If you guessed avian flu, you're wrong. It's measles.

True, avian flu has the world in a pandemic panic. But it is not yet easily transmitted between people, and there have been just 225 confirmed human cases. At this time, the Centers for Disease Control and Prevention is not recommending travel restrictions because of flu concerns.

A number of overlooked health threats are much more likely to afflict travelers, says Phyllis Kozarsky, an infectious disease specialist and consultant to the CDC. (A country-by-country list of warnings is at cdc.gov/travel.)

Measles.In June, the CDC warned travelers bound for World Cup matches in Germany to make sure they were up to date on measles shots because of outbreaks near three cities that would host matches. The disease is more common overseas, where vaccination guidelines are less strict. Americans born before 1957 are assumed to have been exposed to the virus and developed immunity. Post-1957-ers heading abroad should check medical records. If you haven't been immunized or aren't sure, the CDC recommends a vaccination: two shots, at least four weeks apart.

Malaria. Worldwide, malaria infects more than 300 million people every year and kills 1 million. Although it was wiped out in the United States after World War II, there were 1,300 cases last year, mostly travelers returning from the tropics, from sub-Saharan Africa to South America to Asia (though a U.S. traveler was infected this spring in an unusual outbreak in the Bahamas). Malaria, which initially causes fever and flulike symptoms, can lead to anemia, multiple organ failure, and death. Caused by a parasite that lives in the anopheles mosquito's salivary glands, it's curable if treated promptly. Because the disease may not appear for months after infection, people who develop fever and chills later on may not make the malaria connection. Taking antimalarial drugs while traveling won't stop you from getting infected but generally prevents the malarial parasite from developing in your blood. The traveler's health area of CDC's website has information about the type of malaria medication appropriate for different areas.

Dengue fever. Mosquitoes get the blame for this tropical virus as well. After being mostly invisible for decades in this hemisphere, dengue fever has begun reappearing in Central and South America. It is often called "break-bone fever" because sufferers feel, in addition to chills and fever, as if every bone in their body is broken. There is no pill or vaccine to prevent it. Stay covered and use a good insect repellent (story on Page 57).

Hepatitis B and other sexually transmitted diseases. Vacationers often let down their hair and their guard. And that can be hazardous. If you worry that your impulses may get the better of common sense, a hepatitis B vaccine will protect you against this virus, which is passed through blood and bodily fluids. But safe sex is your best protection.

Preventive Plans A, B, C & D

Here's your vacation medical to-do list. Anything you're packing should go in carry-on luggage.

See the doc. Overseas-bound? Visit four to six weeks before departure to discuss immunizations and meds you start prior to takeoff, like antimalarial pills. Also: Get (and fill) a prescription for an antibiotic for traveler's or infectious diarrhea.

Prepare a first-aid kit. Include aspirin, ibuprofen, and Pepto-Bismol, which may help ward off or treat traveler's diarrhea. Drop in the antidiarrhea antibiotic, too. If you have allergies, bring epinephrine and an antihistamine like Benadryl.

Stock up on regular meds. Buy enough to last the trip, with extra for delays or loss. Bring a list of each, the dose, and generic name.

Consider travel insurance. Policies typically cost 4 to 8 percent of the trip tab and cover cancellation/interruption and medical/evacuation needs. Consider a policy if you're headed to a remote spot or if you have health issues. At insuremytrip.com, you can compare many policies.