Thank you for reading my story and for your insightful comment. Amazing that at my age I can be excited by these ideas and the prospect of writing them down!
All the points you mention are good areas to explore. The danger of contagion, priorities, the risk of remaining vs. leaving--all of these have potential for conflict.
I think the charm of science fiction is that it blends reality with imagination. Fantasy (which I also like) doesn't require the writer to tether the material. Science fiction demands a little more.
The second chapter is already begun... actually, it was part of this story but my son advised me to leave it, and he was right.
Thank you, again, for your encouragement. I think I will write this and publish it here even if people don't read it.