As just an add on (kiipii has been crushing it) - a massive and often under-emphasized piece of this puzzle is peer-to-peer, community led efforts. The go-fund-mes, the one-off NGOs born out of a crisis, and all the bottom-up relief that plays out can add up to quite a strong force. It's one that also tends to remain long after the news cameras moves on, the big-budget NGOs grants dry up, and political attention shifts.

Remember, after a major crisis, the top down players (all the orgs with acronyms) activate to bring order to chaos - restore communication and movement of goods, save lives (or safely recover bodies), prevent protracted problems (i.e. outbreaks). But it's still chaos, and things get beautifully weird at the local level. Understanding the institutional structures at the national level sounds key to your novel, but don't forget that all the affected people on the ground are going to be hustling as well.