Travelers Aid has heard heartbreaking stories from people who have traveled abroad and then had a serious accident or medical incident (stroke, heart attack) causing lengthy hospitalization and requiring medical evacuation to return to the US. Most US health insurance plans (including Medicare and Medicaid) DO NOT cover foreign hospitalization or medical care. Medical evacuation can cost tens of thousands of dollars! Before traveling abroad, we recommend that you purchase travel medical insurance (check with your insurance carrier) that includes medical evacuation. This simple step can give you peace of mind.
Also, please take a look at all of the tips from the US State Department for foreign travel: http://travel.state.gov/travel/tips/tips_1232.html