Something I consider a very real concern is a severe and deadly flu. I used to do HIV work and hang out with infectious disease docs. You ask them of the likelihood of a repeat of the 1918 flu pandemic and they say "it's a question of when, not if."
The Matt Damon movie "Contagion" gave a good flavor of some of the problems that will arise.
This is what drives my food storage. I figure I have about 3 weeks of regular food and another 2,3 months of long term food stored. Figure it will give us a fighting chance.