Travel Health Insurance
The prospect of getting sick or being injured while travelling is one of the things that, unfortunately, keeps many people at home. It is a risk, no question, but you can mitigate some of the risk by purchasing travel health insurance. As mentioned in the previous post, check with your credit card company to see if health insurance is included, and if so for how long.
There is a post on http://thyblackman.com/2014/08/22/how-to-find-travel-insurance-in-a-budget/ has some interesting suggestions about checking into specific types of insurance aimed at students, seniors, or practicioners of certain high-risk sports. It also recommends speaking with a travel agent who specializes in this kind of coverage and looking into insurance that may be provided by the volunteer project you are joining, if you travel to volunteer.
The thing to remember about travel health insurance is that it is in the company's interest to interpret your coverage very narrowly. I recently purchased health insurance from a company I will not name, and was surprised to find that it would not cover me for a potentially life-threatening reaction to a prescription drug, because the drug was to treat a pre-existing condition. And remember, the companies have full access to your medical records.
Another time I was travelling to an area considered a war zone, and was told my insurance coverage would not be operative. "Even if I just fell at the hotel and broke my ankle?" I asked. I was told it would be decided on a case-by-case basis, probably another way of saying no, I would not be insured.
The country where it is most important to have medical insurance is the United States. The medical care in the U.S. is world class, but so are the prices. However, if you are visiting the U.S. and do not have insurance, remember that hospitals are required by federal law to treat you for life-threatening conditions regardless of your insurance coverage or ability to pay.
Of course, the hospital will try to collect for the cost of your care afterwards, most likely at highly inflated prices (don't ask,) but if you are a foreign resident with no assets in the U.S. they may have trouble doing so. I am not advocating avoiding paying your debts, but the U.S. system is so complex and so expensive that you may not be able to do so.