How could humans survive underground for centuries? People have built multiple underground facilities around the world to prepare for a catastrophe. Just to be careful they overcalculated their resource needs. However they didn't expect their surface samples to contain a new deadly disease. They decide to wait out the disease, but this takes centuries, maybe even a millennium.
How would these people live sustainable? What would they eat? How could they expand? Also what about sunlight and other problems?
Imagine a late 21st century civilisation, about 50 years from now.
The groups that went underground are the elite, as such they consist mainly of scientists and rich folks. Billions of dollars go into the creation of these facilities.
Multiple hundreds of people should fit in one facillity.
They had enough time to prepare so they might have some livestock and vegetables. Maybe they could practice some form of underground agriculture?
The disease is vaccine proof, so "vaccine and resurface" solutions are not possible. I already have a way to keep it alive on surface so also no "wait until the disease has no host and dies out" answer works.
I just need to know how they would stay sustainable for a thousand years.
This answer seems to already solve how to get water although is this still possible with an air + waterborne disease?