Regular travel medical insurance works in safe places under normal conditions. Translation: it doesn’t work in disaster areas.
First of all, congratulations for being a fantastic human.
General travel medical insurance doesn’t cover places that carry government warnings. This includes places that have serious damage due to natural disasters and areas with unstable governments.
Finding adequate medical treatment in an area with no electricity or infrastructure isn’t just a challenge, it’s expensive.
Humanitarian insurance covers medical costs incurred outside government Safe Travel lists. Many plans offer emergency medical evacuation and coverage in case of war or terrorism.
If you answer yes to the following question, you need it. Are you going somewhere to provide humanitarian aid?
For people travelling in groups, check with the event leader. Groups can take advantage of discount for bulk-purchases, and often get some freebies thrown in, like baggage deals and cheaper transport.
For individuals, check out some policies before you nix the idea. Consider the infrastructure of your destination. How it might degrade during your stay. Even if the lights are back on, will they survive another storm? Are the people running the hospitals reliable? What about medical supplies? Is the government stable? What happens if there’s a terrorist act?
Can’t make up your mind? Most aid organisations require proof of insurance before you can join them. This keeps the aid going to the needy, not to needy volunteers.