OK. I always wanted to be one of the first posters in a new forum.
What I see as THE most critical issue?
WATER.
Water sanitation is responsible for saving more lives than anything else.
Number two? Antibiotics.
In Corps School, (many many moons ago) I remember hearing a bit of info that really stood out - WW II was the FIRST time in war more people were lost to actual enemy action than disease.