for countries affected by natural disasters, many (in the americas at least) have most of the supplies they need already in the country. this is contrary to what the news media often reports. ironically, this causes many well-meaning people to send donations to places where they may not be drastically needed. also, field hospitals that are already in the country can usually be set up much faster than waiting on other countries to send field hospitals. for those countries who do not have these resources, one of the items highest on their list of things to have in case of emergency are field hospitals.